SANTANDER UK GROUP HOLDINGS PLC (SEC Filing Page | XBRL Cloud Viewer | XBRL Instance)

Line Label Object Class Period Type Balance Report ElementName
1 1001 - Document - Document and Entity Information Network

*

*

 http://santander.co.uk/taxonomy/role/DocumentandEntityInformation
2 Implied Table Table

*

*

 implied:Table
3 Document and entity information [abstract] Abstract ck0001649373:DocumentAndEntityInformationAbstract
4 Document Type Concept (Submission Type) For Period dei:DocumentType
5 Amendment Flag Concept (Yes/No) For Period dei:AmendmentFlag
6 Document Period End Date Concept (Date) For Period dei:DocumentPeriodEndDate
7 Document Fiscal Year Focus Concept (Year) For Period dei:DocumentFiscalYearFocus
8 Document Fiscal Period Focus Concept (Fiscal Period) For Period dei:DocumentFiscalPeriodFocus
9 Trading Symbol Concept (Text/String) For Period dei:TradingSymbol
10 Entity Registrant Name Concept (Text/String) For Period dei:EntityRegistrantName
11 Entity Central Index Key Concept (CIK Number) For Period dei:EntityCentralIndexKey
12 Current Fiscal Year End Date Concept (Month/Day) For Period dei:CurrentFiscalYearEndDate
13 Entity Well-known Seasoned Issuer Concept (Yes/No) For Period dei:EntityWellKnownSeasonedIssuer
14 Entity Current Reporting Status Concept (Yes/No) For Period dei:EntityCurrentReportingStatus
15 Entity Filer Category Concept (Filer Category) For Period dei:EntityFilerCategory
16 Entity Shell Company Concept (Yes/No) For Period dei:EntityShellCompany
17 Entity Emerging Growth Company Concept (Yes/No) For Period dei:EntityEmergingGrowthCompany
18 Entity Common Stock, Shares Outstanding Concept (Shares) As Of dei:EntityCommonStockSharesOutstanding
19 1003 - Statement - Consolidated Income Statement Network

*

*

 http://santander.co.uk/taxonomy/role/NotesAnalysisOfIncomeAndExpense-800200
20 Implied Table Table

*

*

 implied:Table
21 Profit or loss [abstract] Abstract ifrs-full:IncomeStatementAbstract
22 Profit (loss) [abstract] Abstract ifrs-full:ProfitLossAbstract
23 Interest and similar income Concept (Monetary) For Period Credit ifrs-full:RevenueFromInterest
24 Interest expense and similar charges Concept (Monetary) For Period Debit ifrs-full:InterestExpense
25 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestRevenueExpense
26 Fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncome
27 Fee and commission expense Concept (Monetary) For Period Debit ifrs-full:FeeAndCommissionExpense
28 Net fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncomeExpense
29 Net trading and other income Concept (Monetary) For Period Credit ck0001649373:NetTradingAndOtherIncome
30 Total operating income Concept (Monetary) For Period Credit ifrs-full:RevenueAndOperatingIncome
31 Operating expenses before credit impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001649373:OperatingExpensesBeforeCreditImpairmentLossesProvisionsAndCharges
32 Credit impairment losses Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
33 Provisions for other liabilities and charges Concept (Monetary) For Period Debit ck0001649373:ProvisionsForOtherLiabilitiesAndCharges
34 Total operating credit impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001649373:AggregateOperatingCreditImpairmentLossesProvisionsAndCharges
35 Profit before tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
36 Tax on profit Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
37 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
38 Attributable to: Abstract ifrs-full:ProfitLossAttributableToAbstract
39 Equity holders of the parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
40 Non-controlling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
41 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
42 1004 - Statement - Consolidated Statement of Comprehensive Income Network

*

*

 http://santander.co.uk/taxonomy/role/StatementOfComprehensiveIncomeOCIComponentsPresentedNetOfTax-410000
43 Implied Table Table

*

*

 implied:Table
44 Statement of comprehensive income [abstract] Abstract ifrs-full:StatementOfComprehensiveIncomeAbstract
45 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
46 Other comprehensive income: Abstract ifrs-full:OtherComprehensiveIncomeAbstract
47 Other comprehensive income that may be reclassified to profit or loss subsequently: Abstract ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTaxAbstract
48 Available-for-sale securities: Abstract ifrs-full:AvailableforsaleFinancialAssetsAbstract
49 - Change in fair value Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnRemeasuringAvailableforsaleFinancialAssetsBeforeTax
50 - Income statement transfers Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnAvailableforsaleFinancialAssetsBeforeTax
51 - Taxation Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToAvailableforsaleFinancialAssetsOfOtherComprehensiveIncome
52 Other comprehensive income available-for-sale securities, total Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxAvailableforsaleFinancialAssets
53 Movement in fair value reserve (debt instruments): Abstract ifrs-full:FinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeAbstract
54 - Change in fair value Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeBeforeTax
55 - Income statement transfers Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeBeforeTax
56 - Taxation Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncome
57 Other comprehensive income fair value reserve (debt instruments) Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeNetOfTax
58 Cash flow hedges: Abstract ifrs-full:CashFlowHedgesAbstract
59 - Effective portion of changes in fair value Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax
60 - Income statement transfers Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax
61 - Taxation Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome
62 Other comprehensive income cash flow hedges, total Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxCashFlowHedges
63 Currency translation on foreign operations Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationNetOfTax
64 Net other comprehensive income that may be reclassified to profit or loss subsequently Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTax
65 Other comprehensive income that will not be reclassified to profit or loss subsequently: Abstract ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTaxAbstract
66 Pension remeasurement: Abstract ck0001649373:PensionRemeasurementAbstract
67 - Change in fair value Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
68 - Taxation Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome
69 Pension remeasurement, total Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
70 Own credit adjustment: Abstract ck0001649373:ChangeInFairValueOfFinancialLiabilityAttributableToChangeInCreditRiskOfLiabilityAbstract
71 - Change in fair value Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxChangeInFairValueOfFinancialLiabilityAttributableToChangeInCreditRiskOfLiability
72 - Taxation Concept (Monetary) For Period Debit ifrs-full:IncomeTaxRelatingToChangesInFairValueOfFinancialLiabilityAttributableToChangeInCreditRiskOfLiabilityOfOtherComprehensiveIncome
73 Own credit adjustment, total Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxChangeInFairValueOfFinancialLiabilityAttributableToChangeInCreditRiskOfLiability
74 Net other comprehensive income that will not be reclassified to profit or loss subsequently Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTax
75 Total other comprehensive income net of tax Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncome
76 Total comprehensive income Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
77 Attributable to: Abstract ifrs-full:ComprehensiveIncomeAttributableToAbstract
78 Equity holders of the parent Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToOwnersOfParent
79 Non-controlling interests Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToNoncontrollingInterests
80 Total comprehensive income Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
81 1005 - Statement - Consolidated Balance Sheet Network

*

*

 http://santander.co.uk/taxonomy/role/StatementOfFinancialPositionOrderOfLiquidity-220000
82 Statement [table] Table

*

*

 ck0001649373:StatementTable
83 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
84 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
85 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
86 Statement [LineItems] LineItems ck0001649373:StatementLineItems
87 Assets Abstract ifrs-full:AssetsAbstract
88 Cash and balances at central banks Concept (Monetary) As Of Debit ifrs-full:CashAndBankBalancesAtCentralBanks
89 Financial assets at fair value through profit or loss: Abstract ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossAbstract
90 - Trading assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
91 - Derivative financial instruments Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
92 - Other financial assets at fair value through profit or loss Concept (Monetary) As Of Debit ck0001649373:OtherFinancialAssetsAtFairValueThroughProfitOrLoss
93 Financial assets at amortised cost Abstract ck0001649373:FinancialAssetsAtAmortisedCostAbstract
94 - Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
95 - Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
96 - Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
97 Other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001649373:OtherFinancialAssetsAtAmortisedCost
98 - Other financial assets at amortised cost Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtAmortisedCost
99 Financial assets at fair value through other comprehensive income Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
100 Financial investments Concept (Monetary) As Of Debit ck0001649373:FinancialInvestments
101 Interests in other entities Concept (Monetary) As Of Debit ifrs-full:InvestmentsInSubsidiariesJointVenturesAndAssociates
102 Intangible assets Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsAndGoodwill
103 Property, plant and equipment Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
104 Current tax assets Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssets
105 Retirement benefit assets Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsDefinedBenefitPlan
106 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
107 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
108 Liabilities Abstract ifrs-full:LiabilitiesAbstract
109 Financial liabilities at fair value through profit or loss: Abstract ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossAbstract
110 - Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
111 - Derivative financial instruments Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
112 - Other financial liabilities at fair value through profit or loss Concept (Monetary) As Of Credit ck0001649373:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
113 Financial liabilities at amortised cost Abstract ck0001649373:FinancialLiabilitiesAtAmortisedCostAbstract
114 - Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
115 - Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
116 - Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
117 - Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
118 - Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
119 Other liabilities Concept (Monetary) As Of Credit ifrs-full:OtherLiabilities
120 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
121 Current tax liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilities
122 Deferred tax liabilities Concept (Monetary) As Of Credit ifrs-full:NetDeferredTaxLiabilities
123 Retirement benefit obligations Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
124 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
125 Equity Abstract ifrs-full:EquityAbstract
126 Share capital Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
127 Other equity instruments Concept (Monetary) As Of Credit ifrs-full:OtherEquityInterest
128 Retained earnings Concept (Monetary) As Of Credit ifrs-full:RetainedEarnings
129 Other reserves Concept (Monetary) As Of Credit ifrs-full:OtherReserves
130 Total shareholders' equity Concept (Monetary) As Of Credit ifrs-full:EquityAttributableToOwnersOfParent
131 Non-controlling interests Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
132 Total equity Concept (Monetary) As Of Credit ifrs-full:Equity
133 Total liabilities and equity Concept (Monetary) As Of Credit ifrs-full:EquityAndLiabilities
134 1006 - Statement - Consolidated Cash Flow Statement Network

*

*

 http://santander.co.uk/taxonomy/role/StatementOfCashFlowsIndirectMethod-520000
135 Statement [table] Table

*

*

 ck0001649373:StatementTable
136 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
137 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
138 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
139 Statement [LineItems] LineItems ck0001649373:StatementLineItems
140 Cash flows from operating activities Abstract ifrs-full:CashFlowsFromUsedInOperatingActivitiesAbstract
141 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
142 Non-cash items included in profit: Abstract ifrs-full:AdjustmentsForReconcileProfitLossAbstract
143 - Depreciation and amortisation Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDepreciationAndAmortisationExpense
144 - Provisions for other liabilities and charges Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForProvisions
145 - Impairment losses Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLoss
146 - Corporation tax charge Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncomeTaxExpense
147 - Other non-cash items Concept (Monetary) For Period Debit ifrs-full:OtherAdjustmentsForNoncashItems
148 - Pension charge for defined benefit pension schemes Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForPensionChargeForDefinedBenefitPensionSchemes
149 Adjustments to reconcile profit (loss) Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForReconcileProfitLoss
150 Net change in operating assets and liabilities: Abstract ck0001649373:ChangeInOperatingAssetsAndLiabilitiesAbstract
151 - Cash and balances at central banks Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForDecreaseIncreaseInCashAndBalancesAtCentralBanks
152 - Trading assets Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForDecreaseIncreaseInTradingAssets
153 - Derivative assets Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForIncreaseDecreaseInDerivativeAssets
154 - Other financial assets at fair value through profit or loss Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForDecreaseIncreaseInOtherFinancialAssetsAtFairValueThroughProfitOrLoss
155 - Loans and advances to banks and customers Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForDecreaseIncreaseInLoansAndAdvancesToBanksAndCustomers
156 - Other assets Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInOtherAssets
157 - Deposits by banks and customers Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForIncreaseDecreaseInDepositsFromBanksAndCustomers
158 - Derivative liabilities Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForIncreaseDecreaseInDerivativeLiabilities
159 - Trading liabilities Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForIncreaseDecreaseInTradingLiabilities
160 - Other financial liabilities at fair value through profit or loss Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForIncreaseDecreaseInOtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
161 - Debt securities in issue Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForIncreaseDecreaseInDebtSecuritiesInIssue
162 - Other liabilities Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInOtherLiabilities
163 Net change in operating assets and liabilities Concept (Monetary) For Period Debit ck0001649373:AdjustmentsForDecreaseIncreaseInOperatingAssetsAndLiabilities
164 Corporation tax paid Concept (Monetary) For Period Credit ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities
165 Effects of exchange rate differences Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForUnrealisedForeignExchangeLossesGains
166 Net cash flows from operating activities Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperatingActivities
167 Cash flows from investing activities Abstract ifrs-full:CashFlowsFromUsedInInvestingActivitiesAbstract
168 Investments in other entities Concept (Monetary) For Period Credit ifrs-full:CashFlowsUsedInObtainingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
169 Proceeds from disposal of subsidiaries Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
170 Purchase of property, plant and equipment and intangible assets Concept (Monetary) For Period Credit ifrs-full:PurchaseOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
171 Proceeds from sale of property, plant and equipment and intangible assets Concept (Monetary) For Period Debit ifrs-full:ProceedsFromDisposalsOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
172 Purchase of financial investments Concept (Monetary) For Period Credit ck0001649373:PurchasesOfFinancialInvestments
173 Proceeds from sale and redemption of financial investments Concept (Monetary) For Period Debit ck0001649373:ProceedsFromDisposalOrMaturityOfFinancialInvestments
174 Net cash flows from investing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInInvestingActivities
175 Cash flows from financing activities Abstract ifrs-full:CashFlowsFromUsedInFinancingActivitiesAbstract
176 Issue of AT1 Capital Securities Concept (Monetary) For Period Debit ifrs-full:ProceedsFromIssuingOtherEquityInstruments
177 Issuance costs of AT1 Capital Securities Concept (Monetary) For Period Credit ck0001649373:PaymentForOtherEquityInstrumentsIssueCosts
178 Issue of debt securities and subordinated notes Concept (Monetary) For Period Debit ifrs-full:ProceedsFromIssueOfBondsNotesAndDebentures
179 Issuance costs of debt securities and subordinated notes Concept (Monetary) For Period Credit ifrs-full:PaymentsForDebtIssueCosts
180 Repayment of debt securities Concept (Monetary) For Period Credit ifrs-full:RepaymentsOfBondsNotesAndDebentures
181 Repurchase of non-controlling interests Concept (Monetary) For Period Credit ck0001649373:PaymentsForRepurchaseOfNonControllingInterests
182 Dividends paid on ordinary shares Concept (Monetary) For Period Credit ifrs-full:DividendsPaidClassifiedAsFinancingActivities
183 Dividends paid on other equity instruments Concept (Monetary) For Period Credit ck0001649373:DividendsPaidOnOtherEquityInstrumentsClassifiedAsFinancingActivities
184 Dividends paid on non-controlling interests Concept (Monetary) For Period Credit ifrs-full:DividendsPaidToNoncontrollingInterestsClassifiedAsFinancingActivities
185 Net cash flows from financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
186 Change in cash and cash equivalents Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInCashAndCashEquivalentsBeforeEffectOfExchangeRateChanges
187 Cash and cash equivalents at beginning of the year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition
188 Effects of exchange rate changes on cash and cash equivalents Concept (Monetary) For Period Debit ifrs-full:EffectOfExchangeRateChangesOnCashAndCashEquivalents
189 Cash and cash equivalents at the end of the year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition
190 Cash and cash equivalents consist of: Abstract ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPositionAbstract
191 Cash and balances at central banks Concept (Monetary) As Of Debit ifrs-full:CashAndBankBalancesAtCentralBanks
192 Less: regulatory minimum cash balances Concept (Monetary) As Of Debit ifrs-full:MandatoryReserveDepositsAtCentralBanks
193 Cash and bank balances at central banks less regulatory minimum cash balances Concept (Monetary) As Of Debit ifrs-full:BankBalancesAtCentralBanksOtherThanMandatoryReserveDeposits
194 Net trading other cash equivalents Concept (Monetary) As Of Debit ck0001649373:NetTradingAndOtherCashEquivalents
195 Net non-trading other cash equivalents Concept (Monetary) As Of Debit ck0001649373:NetNonTradingOtherCashEquivalents
196 Cash and cash equivalents at the end of the year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition
197 1007 - Statement - Consolidated Cash Flow Statement (Parenthetical) Network

*

*

 http://santander.co.uk/taxonomy/role/StatementOfCashFlowsIndirectMethod-520000Parenthetical
198 Implied Table Table

*

*

 implied:Table
199 Statement of cash flows [abstract] Abstract ifrs-full:StatementOfCashFlowsAbstract
200 Cash consideration received on sale of subsidiaries Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
201 Carrying value of assets and liabilities Concept (Monetary) For Period Debit ck0001649373:CarryingValueOfAssetsAndLiabilitiesOtherThanCashOrCashEquivalentsInSubsidiary
202 1008 - Statement - Consolidated Statement of Changes in Equity Network

*

*

 http://santander.co.uk/taxonomy/role/StatementOfChangesInEquity-610000
203 Statement of changes in equity [table] Table

*

*

 ifrs-full:StatementOfChangesInEquityTable
204 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
205 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
206 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
207 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
208 Equity [member] Member ifrs-full:EquityMember
209 Share Capital [member] Member ifrs-full:IssuedCapitalMember
210 Other Equity Instruments [member] Member ifrs-full:OtherEquityInterestMember
211 Retained Earnings [member] Member ifrs-full:RetainedEarningsMember
212 Other Reserves Available-For-Sale [member] Member ifrs-full:ReserveOfGainsAndLossesOnRemeasuringAvailableforsaleFinancialAssetsMember
213 Other Reserves Fair Value Reserves [member] Member ifrs-full:ReserveOfGainsAndLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember
214 Other Reserves Cash Flow Hedging [member] Member ifrs-full:ReserveOfCashFlowHedgesMember
215 Other Reserves Currency Translation [member] Member ifrs-full:ReserveOfExchangeDifferencesOnTranslationMember
216 Total [member] Member ifrs-full:EquityAttributableToOwnersOfParentMember
217 Non-Controlling Interests [member] Member ifrs-full:NoncontrollingInterestsMember
218 Statement of changes in equity [line items] LineItems ifrs-full:StatementOfChangesInEquityLineItems
219 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Equity
220 - Profit after tax Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
221 Adoption of IFRS 9 (see Note 1) Concept (Monetary) For Period Debit ck0001649373:AdjustmentForAdoptionOfIFRS9
222 Other comprehensive income, net of tax: Abstract ifrs-full:OtherComprehensiveIncomeAbstract
223 - Available-for-sale securities Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxAvailableforsaleFinancialAssets
224 - Fair value reserve (debt instruments) Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeNetOfTax
225 - Cash flow hedges Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxCashFlowHedges
226 - Pension remeasurement Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
227 - Own credit adjustment Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxChangeInFairValueOfFinancialLiabilityAttributableToChangeInCreditRiskOfLiability
228 - Currency translation on foreign operations Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxExchangeDifferencesOnTranslation
229 Total comprehensive income Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
230 Issue of AT1 capital securities Concept (Monetary) For Period Credit ifrs-full:IssueOfEquity
231 Other Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesEquity
232 Repurchase of non-controlling interests Concept (Monetary) For Period Debit ck0001649373:RepurchaseOfNoncontrollingInterests
233 Dividends on ordinary shares Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToOwnersOfParent
234 Dividends on other equity instruments Concept (Monetary) For Period Debit ck0001649373:DividendsRecognisedOnOtherEquityInstruments
235 Dividends on non-controlling interests Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToNoncontrollingInterests
236 Tax on non-controlling interests and other equity instruments Concept (Monetary) For Period Debit ck0001649373:TaxOnNoncontrollingInterestsAndOtherEquityInstruments
237 Ending balance Concept (Monetary) As Of Credit ifrs-full:Equity
238 1009 - Disclosure - Risk Framework Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialRiskManagementExplanatory
239 Implied Table Table

*

*

 implied:Table
240 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
241 Risk Framework Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialRiskManagementExplanatory
242 1010 - Disclosure - Credit risk Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCreditRiskExplanatory
243 Implied Table Table

*

*

 implied:Table
244 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
245 Credit risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCreditRiskExplanatory
246 1011 - Disclosure - Market risk Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfMarketRiskExplanatory
247 Implied Table Table

*

*

 implied:Table
248 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
249 Market risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfMarketRiskExplanatory
250 1012 - Disclosure - Liquidity risk Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfLiquidityRiskExplanatory
251 Implied Table Table

*

*

 implied:Table
252 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
253 Liquidity risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfLiquidityRiskExplanatory
254 1013 - Disclosure - Capital risk Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCapitalRiskExplanatory
255 Implied Table Table

*

*

 implied:Table
256 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
257 Capital risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCapitalRiskExplanatory
258 1014 - Disclosure - Accounting Policies Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
259 Statement [table] Table

*

*

 ck0001649373:StatementTable
260 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
261 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
262 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
263 Statement [LineItems] LineItems ck0001649373:StatementLineItems
264 Accounting Policies Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
265 1015 - Disclosure - Segments Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfEntitysReportableSegmentsExplanatory
266 Implied Table Table

*

*

 implied:Table
267 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
268 Segments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEntitysReportableSegmentsExplanatory
269 1016 - Disclosure - Net Interest Income Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfInterestIncomeExpenseExplanatory
270 Implied Table Table

*

*

 implied:Table
271 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
272 Net Interest Income Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestIncomeExpenseExplanatory
273 1017 - Disclosure - Net Fee and Commission Income Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFeeAndCommissionIncomeExpenseExplanatory
274 Implied Table Table

*

*

 implied:Table
275 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
276 Net Fee and Commission Income Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFeeAndCommissionIncomeExpenseExplanatory
277 1018 - Disclosure - Net Trading and Other Income Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfTradingIncomeExpenseAndOtherOperatingIncomeExpenseExplanatory
278 Implied Table Table

*

*

 implied:Table
279 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
280 Net Trading and Other Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTradingIncomeExpenseAndOtherOperatingIncomeExpenseExplanatory
281 1019 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfExpensesExplanatory
282 Statement [table] Table

*

*

 ck0001649373:StatementTable
283 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
284 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
285 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
286 Statement [LineItems] LineItems ck0001649373:StatementLineItems
287 Operating Expenses Before Credit Impairment Losses, Provisions and Charges Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfExpensesExplanatory
288 1020 - Disclosure - Audit and Other Services Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfAuditorsRemunerationExplanatory
289 Implied Table Table

*

*

 implied:Table
290 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
291 Audit and Other Services Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAuditorsRemunerationExplanatory
292 1021 - Disclosure - Credit Impairment Losses and Provisions Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfImpairmentLossesOnFinancialAssetsAndProvisionsExplanatory
293 Implied Table Table

*

*

 implied:Table
294 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
295 Credit Impairment Losses and Provisions Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfImpairmentLossesOnFinancialAssetsAndProvisionsExplanatory
296 1022 - Disclosure - Taxation Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfIncomeTaxAndDeferredTaxesExplanatory
297 Implied Table Table

*

*

 implied:Table
298 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
299 Taxation Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfIncomeTaxAndDeferredTaxesExplanatory
300 1023 - Disclosure - Dividends on Ordinary Shares Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDividendsExplanatory
301 Statement [table] Table

*

*

 ck0001649373:StatementTable
302 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
303 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
304 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
305 Statement [LineItems] LineItems ck0001649373:StatementLineItems
306 Dividends on Ordinary Shares Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDividendsExplanatory
307 1024 - Disclosure - Trading Assets Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialAssetsHeldForTradingExplanatory
308 Implied Table Table

*

*

 implied:Table
309 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
310 Trading Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsHeldForTradingExplanatory
311 1025 - Disclosure - Derivative Financial Instruments Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDerivativeFinancialInstrumentsExplanatory
312 Implied Table Table

*

*

 implied:Table
313 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
314 Derivative Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDerivativeFinancialInstrumentsExplanatory
315 1026 - Disclosure - Other Financial Assets At Fair Value Through Profit Or Loss Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatory
316 Implied Table Table

*

*

 implied:Table
317 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
318 Other Financial Assets At Fair Value Through Profit Or Loss Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatory
319 1027 - Disclosure - Loans and Advances to Customers Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfLoansAndAdvancesToCustomersExplanatory
320 Implied Table Table

*

*

 implied:Table
321 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
322 Loans and Advances to Customers Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfLoansAndAdvancesToCustomersExplanatory
323 1028 - Disclosure - Securitisations and Covered Bonds Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSecuritisationsAndCoveredBondsExplanatory
324 Implied Table Table

*

*

 implied:Table
325 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
326 Securitisations and Covered Bonds Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfSecuritisationsAndCoveredBondsExplanatory
327 1029 - Disclosure - Transfers of Financial Assets Not Qualifying for Derecognition Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialAssetsTransferredDuringPeriodWhichDoNotQualifyForDerecognitionExplanatory
328 Implied Table Table

*

*

 implied:Table
329 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
330 Transfers of Financial Assets Not Qualifying for Derecognition Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsTransferredDuringPeriodWhichDoNotQualifyForDerecognitionExplanatory
331 1030 - Disclosure - Reverse Repurchase Agreements - Non Trading Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfReverseRepurchaseAgreementsNontradingExplanatory
332 Statement [table] Table

*

*

 ck0001649373:StatementTable
333 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
334 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
335 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
336 Statement [LineItems] LineItems ck0001649373:StatementLineItems
337 Reverse Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfReverseRepurchaseAgreementsNontradingExplanatory
338 1031 - Disclosure - Other Financial Assets At Amortised Cost Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherFinancialAssetsAtAmortisedCostExplanatory
339 Statement [table] Table

*

*

 ck0001649373:StatementTable
340 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
341 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
342 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
343 Statement [LineItems] LineItems ck0001649373:StatementLineItems
344 Other Financial Assets At Amortised Cost Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherFinancialAssetsAtAmortisedCostExplanatory
345 1032 - Disclosure - Financial Assets At Fair Value Through Other Comprehensive Income Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatory
346 Implied Table Table

*

*

 implied:Table
347 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
348 Financial Assets At Fair Value Through Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatory
349 1033 - Disclosure - Financial Investments Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInvestmentsExplanatory
350 Statement [table] Table

*

*

 ck0001649373:StatementTable
351 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
352 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
353 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
354 Statement [LineItems] LineItems ck0001649373:StatementLineItems
355 Financial Investments Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfFinancialInvestmentsExplanatory
356 1034 - Disclosure - Interests in Other Entities Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfInterestsInOtherEntitiesExplanatory
357 Statement [table] Table

*

*

 ck0001649373:StatementTable
358 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
359 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
360 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
361 Statement [LineItems] LineItems ck0001649373:StatementLineItems
362 Interests in Other Entities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestsInOtherEntitiesExplanatory
363 1035 - Disclosure - Intangible Assets Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfIntangibleAssetsAndGoodwillExplanatory
364 Implied Table Table

*

*

 implied:Table
365 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
366 Intangible Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIntangibleAssetsAndGoodwillExplanatory
367 1036 - Disclosure - Trading Liabilities Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialLiabilitiesHeldForTradingExplanatory
368 Implied Table Table

*

*

 implied:Table
369 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
370 Trading Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialLiabilitiesHeldForTradingExplanatory
371 1037 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossExplanatory
372 Implied Table Table

*

*

 implied:Table
373 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
374 Other Financial Liabilities at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossExplanatory
375 1038 - Disclosure - Deposits by Customers Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDepositsFromCustomersExplanatory
376 Implied Table Table

*

*

 implied:Table
377 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
378 Deposits by Customers Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDepositsFromCustomersExplanatory
379 1039 - Disclosure - Deposits by Banks Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDepositsFromBanksExplanatory
380 Statement [table] Table

*

*

 ck0001649373:StatementTable
381 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
382 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
383 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
384 Statement [LineItems] LineItems ck0001649373:StatementLineItems
385 Deposits by Banks Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDepositsFromBanksExplanatory
386 1040 - Disclosure - Repurchase Agreements - Non Trading Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfRepurchaseAgreementsNontradingExplanatory
387 Implied Table Table

*

*

 implied:Table
388 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
389 Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfRepurchaseAgreementsNontradingExplanatory
390 1041 - Disclosure - Debt Securities in Issue Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDebtSecuritiesExplanatory
391 Statement [table] Table

*

*

 ck0001649373:StatementTable
392 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
393 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
394 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
395 Statement [LineItems] LineItems ck0001649373:StatementLineItems
396 Debt Securities in Issue Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDebtSecuritiesExplanatory
397 1042 - Disclosure - Subordinated Liabilities Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSubordinatedLiabilitiesExplanatory
398 Statement [table] Table

*

*

 ck0001649373:StatementTable
399 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
400 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
401 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
402 Statement [LineItems] LineItems ck0001649373:StatementLineItems
403 Subordinated Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSubordinatedLiabilitiesExplanatory
404 1043 - Disclosure - Provisions Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfProvisionsExplanatory
405 Implied Table Table

*

*

 implied:Table
406 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
407 Provisions Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfProvisionsExplanatory
408 1044 - Disclosure - Retirement Benefit Plans Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfEmployeeBenefitsExplanatory
409 Implied Table Table

*

*

 implied:Table
410 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
411 Retirement Benefit Plans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEmployeeBenefitsExplanatory
412 1045 - Disclosure - Contingent Liabilities And Commitments Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCommitmentsAndContingentLiabilitiesExplanatory
413 Statement [table] Table

*

*

 ck0001649373:StatementTable
414 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
415 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
416 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
417 Statement [LineItems] LineItems ck0001649373:StatementLineItems
418 Contingent Liabilities And Commitments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCommitmentsAndContingentLiabilitiesExplanatory
419 1046 - Disclosure - Share Capital Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfIssuedCapitalExplanatory
420 Statement [table] Table

*

*

 ck0001649373:StatementTable
421 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
422 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
423 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
424 Statement [LineItems] LineItems ck0001649373:StatementLineItems
425 Share Capital Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIssuedCapitalExplanatory
426 1047 - Disclosure - Other Equity Instruments Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherEquityInstrumentsExplanatory
427 Statement [table] Table

*

*

 ck0001649373:StatementTable
428 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
429 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
430 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
431 Statement [LineItems] LineItems ck0001649373:StatementLineItems
432 Other Equity Instruments Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherEquityInstrumentsExplanatory
433 1048 - Disclosure - Non-Controlling Interests Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfNoncontrollingInterestsExplanatory
434 Implied Table Table

*

*

 implied:Table
435 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
436 Non-Controlling Interests Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNoncontrollingInterestsExplanatory
437 1049 - Disclosure - Changes in Liabilities Arising from Financing Activities Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfReconciliationOfLiabilityArisingFromFinancingActivitiesExplanatory
438 Statement [table] Table

*

*

 ck0001649373:StatementTable
439 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
440 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
441 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
442 Statement [LineItems] LineItems ck0001649373:StatementLineItems
443 Changes in Liabilities Arising from Financing Activities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfReconciliationOfLiabilityArisingFromFinancingActivitiesExplanatory
444 1050 - Disclosure - Assets Charged As Security For Liabilities And Collateral Accepted As Security For Assets Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCollateralExplanatory
445 Implied Table Table

*

*

 implied:Table
446 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
447 Assets Charged As Security For Liabilities And Collateral Accepted As Security For Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCollateralExplanatory
448 1051 - Disclosure - Share-Based Compensation Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSharebasedPaymentArrangementsExplanatory
449 Implied Table Table

*

*

 implied:Table
450 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
451 Share-Based Compensation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSharebasedPaymentArrangementsExplanatory
452 1052 - Disclosure - Transactions With Directors and Other Key Management Personnel Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfInformationAboutKeyManagementPersonnelExplanatory
453 Statement [table] Table

*

*

 ck0001649373:StatementTable
454 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
455 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
456 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
457 Statement [LineItems] LineItems ck0001649373:StatementLineItems
458 Transactions With Directors and Other Key Management Personnel Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationAboutKeyManagementPersonnelExplanatory
459 1053 - Disclosure - Related Party Disclosures Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfRelatedPartyExplanatory
460 Statement [table] Table

*

*

 ck0001649373:StatementTable
461 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
462 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
463 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
464 Statement [LineItems] LineItems ck0001649373:StatementLineItems
465 Related Party Disclosures Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRelatedPartyExplanatory
466 1054 - Disclosure - Financial Instruments Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInstrumentsExplanatory
467 Implied Table Table

*

*

 implied:Table
468 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
469 Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsExplanatory
470 1055 - Disclosure - Offsetting Financial Assets and Liabilities Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOffsettingOfFinancialAssetsAndFinancialLiabilitiesExplanatory
471 Implied Table Table

*

*

 implied:Table
472 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
473 Offsetting Financial Assets and Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOffsettingOfFinancialAssetsAndFinancialLiabilitiesExplanatory
474 1056 - Disclosure - Ring-Fencing Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfRingFencingExplanatory
475 Implied Table Table

*

*

 implied:Table
476 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
477 Ring-Fencing Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfRingFencingExplanatory
478 1057 - Disclosure - Transition to IFRS 9 Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfImpactOfAdoptionOfIFRS9Explanatory
479 Implied Table Table

*

*

 implied:Table
480 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
481 Transition to IFRS 9 Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfImpactOfAdoptionOfIFRS9Explanatory
482 1058 - Disclosure - Events After the Balance Sheet Date Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfEventsAfterReportingPeriodExplanatory
483 Statement [table] Table

*

*

 ck0001649373:StatementTable
484 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
485 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
486 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
487 Statement [LineItems] LineItems ck0001649373:StatementLineItems
488 Events After the Balance Sheet Date Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEventsAfterReportingPeriodExplanatory
489 1059 - Disclosure - Loans and Advances to Banks Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfLoansAndAdvancesToBanksExplanatory
490 Statement [table] Table

*

*

 ck0001649373:StatementTable
491 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
492 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
493 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
494 Statement [LineItems] LineItems ck0001649373:StatementLineItems
495 Loans and Advances to Banks Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfLoansAndAdvancesToBanksExplanatory
496 1060 - Disclosure - Accounting Policies (Policies) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSummaryOfSignificantAccountingPoliciesExplanatoryPolicies
497 Statement [table] Table

*

*

 ck0001649373:StatementTable
498 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
499 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
500 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
501 Statement [LineItems] LineItems ck0001649373:StatementLineItems
502 Basis of preparation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBasisOfPreparationOfFinancialStatementsExplanatory
503 Consolidation Concept (Text Block (HTML)) For Period ck0001649373:DescriptionOfAccountingPolicyForConsolidationTextBlock
504 Foreign currency translation Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForForeignCurrencyTranslationExplanatory
505 Revenue recognition Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForRecognitionOfRevenue
506 Borrowing costs Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForBorrowingCostsExplanatory
507 Pensions and other post-retirement benefits Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForEmployeeBenefitsExplanatory
508 Share-based payments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForSharebasedPaymentTransactionsExplanatory
509 Goodwill and other intangible assets Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIntangibleAssetsAndGoodwillExplanatory
510 Property, plant and equipment Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForPropertyPlantAndEquipmentExplanatory
511 Financial instruments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForFinancialInstrumentsExplanatory
512 Derivative financial instruments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForDerivativeFinancialInstrumentsExplanatory
513 Offsetting financial assets and liabilities Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForOffsettingOfFinancialInstrumentsExplanatory
514 Hedge accounting Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForHedgingExplanatory
515 Impairment of non-financial assets Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForImpairmentOfNonfinancialAssetsExplanatory
516 Leases Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForLeasesExplanatory
517 Income taxes, including deferred taxes Concept (Text Block (HTML)) For Period ck0001649373:DescriptionOfAccountingPolicyForIncomeTaxAndDeferredIncomeTaxExplanatory
518 Cash and cash equivalents Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyToDetermineComponentsOfCashAndCashEquivalents
519 Provisions Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForProvisionsExplanatory
520 Share capital Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIssuedCapitalExplanatory
521 Accounting policies relating to comparatives - IAS 39: Financial Instruments: Recognition and Measurement Concept (Text Block (HTML)) For Period ck0001649373:DescriptionOfAccountingPolicyForFinancialInstrumentsRecognitionAndMeasurementExplanatory
522 Critical Judgements and Accounting Estimates Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAccountingJudgementsAndEstimatesExplanatory
523 1061 - Disclosure - Credit risk (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCreditRiskExplanatoryTables
524 Statement [table] Table

*

*

 ck0001649373:StatementTable
525 Segments [axis] Axis ifrs-full:SegmentsAxis
526 Segments [member] Member ifrs-full:SegmentsMember
527 Mortgages [member] Member ifrs-full:MortgagesMember
528 Other business segments [member] Member ck0001649373:OtherBusinessSegmentsMember
529 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
530 Retail banking [member] Member ck0001649373:RetailBankingMember
531 Consumer (auto) finance [member] Member ck0001649373:ConsumerFinanceMember
532 Business Banking [member] Member ck0001649373:BusinessBankingMember
533 Statement [LineItems] LineItems ck0001649373:StatementLineItems
534 Summary of Annual Growth Rates Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAnnualGrowthRatesForecastExplanatory
535 Summary of Residential Mortgages by Loan Size Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgageLoansByLoanSizeExplanatory
536 Summary of Types of Credit Risk Mitigation Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTypesOfCreditRiskMitigationExplanatory
537 Summary of Exposures to Credit Risk in Business Segments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCreditRiskExposureExplanatory
538 Types Of Customers And HowTo Manage Them Concept (Text Block (HTML)) For Period ck0001649373:TypesOfCustomersAndHowToManageThemExplanatory
539 Summary of Other Segments Exposures by Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherSegmentsExposuresByCreditPerformanceExplanatory
540 Summary of Other Segments by Forbearance Applied Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherSegmentByForbearanceAppliedExplanatory
541 Summary of Commercial Real Estate by Loan to Value Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCommercialRealEstateByLoanToValueExplanatory
542 Summary of Commercial Real Estate by Sector Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCommercialRealEstateBySectorExplanatory
543 Summary of Key Metrics to Measure and Control Credit Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfKeyCreditRiskMetricsExplanatoryExplanatory
544 Summary of Probability Weightings Applied to Scenarios Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosExplanatory
545 Summary of Quantitative Criteria to Measure Significant Increase in Credit Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfQuantitativeCriteriaToMeasureSignificantIncreaseInCreditRiskExplanatory
546 Summary of Qualitative Criteria to Measure Significant Increase in Credit Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfQualitativeCriteriaToMeasureSignificantIncreaseInCreditRiskExplanatory
547 Summary of Difference Between Maximum and Net Exposure to Credit Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDifferenceBetweenMaximumAndNetExposureToCreditRiskExplanatory
548 Summary of Difference Between Maximum and Net Exposure to Credit Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDifferenceBetweenMaximumAndNetExposureToCreditRiskOnAssetsMeasuredAtFVTPLExplanatory
549 Summary of Credit Rating of Financial Assets Subject to Credit Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCreditRatingOfFinancialAssetsSubjectToCreditRiskExplanatory
550 Summary of Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCreditPerformanceExplanatory
551 Summary of IFRS 9 Credit Quality Concept (Text Block (HTML)) For Period ck0001649373:SummaryOfIFRS9CreditQualityExplanatory
552 Summary of Stage 2 Decomposition Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfStageTwoDecompositionExplanatory
553 Summary of Reconciliation of Exposures, ECL and Net Carrying Amounts Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfReconciliationOfExposuresECLAndNetCarryingAmountsExplanatory
554 Summary of ECL Reconciliation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsExplanatory
555 Summary of Country Risk Explosures Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCountryRiskExposuresExplanatory
556 Summary of Balances with Other Banco Santander Companies Concept (Text Block (HTML)) For Period ck0001649373:DisclosuresOfBalancesWithOtherBancoSantanderEntitiesExplanatory
557 Summary of Residential Mortgages by Borrower Profile Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgageLoansByBorrowerProfileExplanatory
558 Summary of Residential Mortgages by Interest Rate Profile Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesByInterestRateProfileExplanatory
559 Summary of Residential Mortgages by Geographical Distribution Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgageLoansByGeographicalDistributionExplanatory
560 Summary of Residential Mortgages by Average Loan Size for New Business Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesByAverageLoanSizeForNewBusinessExplanatory
561 Summary of Residential Mortgages by Loan to Value Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesByLoanToValueExplanatory
562 Summary of Business Banking by Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfBusinessBankingByCreditPerformanceExplanatoryTextBlock
563 Summary of Modification of Loan Terms Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfModificationOfLoanTermsExplanatory
564 Summary of Residential Mortgages by Forbearance Applied Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesByForbearanceAppliedExplanatory
565 Summary of Residential Mortgages Portfolios of Particular Interest by Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesPortfoliosOfParticularInterestByCreditPerformanceExplanatory
566 Summary of Residential Mortgages Portfolios of Particular Interest by Forbearance Applied Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesPortfoliosOfParticularInterestByForbearanceAppliedExplanatory
567 Summary of Consumer (Auto) Finance and Other Unsecured Lending by Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfConsumerAutoFinanceAndOtherUnsecuredLendingByCreditPerformanceExplanatory
568 Summary of Other Segments Exposures By Credit Rating Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherSegmentExposuresByCreditRatingExplanatory
569 Summary of Consumer (Auto) Finance and Other Unsecured Lending By Forbearance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfConsumerAutoFinanceAndOtherUnsecuredLendingByForbearanceExplanatory
570 Summary of Residential Mortgages by Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfResidentialMortgagesbyCreditPerformanceExplanatory
571 Summary of Business Banking by Forbearance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfBusinessBankingByForbearanceExplanatoryTextBlock
572 Summary of Other Segments Exposures by Geographical Distribution Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherSegmentsExposuresByGeographicalDistributionExplanatory
573 Summary of Commercial Real Estate by Credit Performance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCommercialRealEstateByCreditPerformanceExplanatory
574 Social Housing Exposure Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfSocialHousingExposureExplanatory
575 1062 - Disclosure - Market risk (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfMarketRiskExplanatoryTables
576 Implied Table Table

*

*

 implied:Table
577 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
578 Summary of Balance Sheet Allocation by Market Risk Classification Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfBalanceSheetAllocationByMarketRiskClassificationExplanatory
579 Summary of NIM and EVE Sensitivity of Interest Rate Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfNimAndEveSensitivityOfInterestRateRiskExplanatory
580 Summary of Internal VaR for Exposure to Main Classes of Risk Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfInternalVarForExposureToMainClassesOfRiskExplanatory
581 1063 - Disclosure - Liquidity risk (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfLiquidityRiskExplanatoryTables
582 Implied Table Table

*

*

 implied:Table
583 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
584 Summary of Reconciliation of Wholesale Funding to Balance Sheet Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfReconciliationOfWholesaleFundingToBalanceSheetExplanatory
585 Summary of Sources of Wholesale Funding by Maturity Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfWholesaleFundingByMaturityExplanatory
586 Summary of Wholesale Funding by Currency Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCurrencyCompositionOfWholesaleFundingExplanatory
587 Summary of External Term Issuance (Sterling Equivalent) Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTermIssuanceExplanatory
588 Summary of Loan-to-Deposit Ratio Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfLoanToDepositRatioExplanatory
589 1064 - Disclosure - Capital risk (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCapitalRiskExplanatoryTables
590 Implied Table Table

*

*

 implied:Table
591 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
592 Summary of Regulatory Capital Resources Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfRegulatoryCapitalResourcesExplanatory
593 1065 - Disclosure - Accounting Policies (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSummaryOfSignificantAccountingPoliciesExplanatoryTables
594 Implied Table Table

*

*

 implied:Table
595 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
596 Schedule of Useful Lives or Depreciation Rates Used for Property, Plant and Equipment Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfUsefulLivesOrDepreciationRatesPropertyPlantAndEquipmentExplanatory
597 Summary of Probability Weights Applied for Each Scenario of Expected Credit Losses Allowance Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfBaseExpectedCreditLossesToProbabilityWeightedEstimatedCreditLossesExplanatory
598 1066 - Disclosure - Segments (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfEntitysReportableSegmentsExplanatoryTables
599 Implied Table Table

*

*

 implied:Table
600 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
601 Summary of Results by Segment Concept (Text Block (HTML)) For Period ck0001649373:SummaryOfResultsBySegmentExplanatory
602 1067 - Disclosure - Net Interest Income (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfInterestIncomeExpenseExplanatoryTables
603 Implied Table Table

*

*

 implied:Table
604 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
605 Summary of Net Interest Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfNetInterestIncomeExplanatory
606 1068 - Disclosure - Net Fee and Commission Income (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFeeAndCommissionIncomeExpenseExplanatoryTables
607 Implied Table Table

*

*

 implied:Table
608 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
609 Summary of Net Fee and Commission Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfNetFeeAndCommissionIncomeExplanatory
610 1069 - Disclosure - Net Trading and Other Income (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfTradingIncomeExpenseAndOtherOperatingIncomeExpenseExplanatoryTables
611 Implied Table Table

*

*

 implied:Table
612 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
613 Summary of Net Trading and Other Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfNetTradingAndOtherIncomeExplanatory
614 1070 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfExpensesExplanatoryTables
615 Implied Table Table

*

*

 implied:Table
616 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
617 Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOperatingExpensesBeforeImpairmentLossesProvisionsAndChargesExplanatory
618 Summary of Deferred Performance Awards Concept (Text Block (HTML)) For Period ck0001649373:DeferredPerformanceAwardsExplanatory
619 Summary of Amount of Bonus Awarded to Employees Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAmountOfBonusAwardedToEmployeesExplanatory
620 1071 - Disclosure - Audit and Other Services (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfAuditorsRemunerationExplanatoryTables
621 Implied Table Table

*

*

 implied:Table
622 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
623 Summary of Audit and Other Services Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAuditAndOtherServicesExplanatory
624 1072 - Disclosure - Credit Impairment Losses and Provisions (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfImpairmentLossesOnFinancialAssetsAndProvisionsExplanatoryTables
625 Implied Table Table

*

*

 implied:Table
626 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
627 Summary of Impairment Losses and Provisions Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailedInformationOfImpairmentLossesAndProvisionsExplanatory
628 1073 - Disclosure - Taxation (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfIncomeTaxAndDeferredTaxesExplanatoryTables
629 Implied Table Table

*

*

 implied:Table
630 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
631 Disclosure of Tax on Profit Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIncomeTaxExplanatory
632 Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfReconciliationOfChargeResultingFromApplyingUkCorporationTaxRateExplanatory
633 Disclosure of Movements in Current Tax Assets and Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMovementInCurrentTaxAssetsAndLiabilitiesExplanatory
634 Disclosure of Deferred Tax Assets and Liabilities Including Movement in Deferred Tax Account Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDeferredTaxesExplanatory
635 1074 - Disclosure - Dividends on Ordinary Shares (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDividendsExplanatoryTables
636 Implied Table Table

*

*

 implied:Table
637 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
638 Disclosure of Dividends on Ordinary Shares Declared and Paid Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDividendPerOrdinaryShareExplanatory
639 1075 - Disclosure - Trading Assets (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialAssetsHeldForTradingExplanatoryTables
640 Implied Table Table

*

*

 implied:Table
641 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
642 Disclosure of Trading Assets Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTradingAssetsExplanatory
643 1076 - Disclosure - Derivative Financial Instruments (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDerivativeFinancialInstrumentsExplanatoryTables
644 Implied Table Table

*

*

 implied:Table
645 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
646 Notional Amounts and Fair Values of Derivatives Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfNotionalAndFairValueAmountsOfDerivativeFinancialInstrumentsExplanatory
647 Analysis of the Notional and Fair Values of Derivatives by Trading and Settlement Method Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAnalysisOfTheNotionalAndFairValuesOfDerivativesByTradingAndSettlementMethodExplanatory
648 Summary of Fixed Rate Hedged Instruments Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfFixedRateInstrumentsHedgedExplanatory
649 Summary of Possible Sources of Hedge ineffectiveness Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfPossibleSourcesOfHedgeInEffectivenessExplanatory
650 Summary of Maturity Profile and Average Price/Rate of Hedging Instruments Used in Hedging Strategies Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMaturityProfileAndAveragePriceRateOfHedgingInstrumentsUsedInHedgingStrategiesExplanatory
651 Summary of Net Gains Or Losses Arising from Fair Value and Cash Flow Hedges Included in Net Trading and Other Income Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutHedgesExplanatory
652 Summary of Information About Hedging Ineffectiveness by Risk Category Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfInformationAboutHedgingIneffectivenessByRiskCategoryExplanatory
653 Summary of Reconciliation by Risk Category of Components of Equity and Analysis of Other Comprehensive Income Items Resulting from Hedge Accounting Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfReconciliationByRiskCategoryOfComponentsOfEquityAndAnalysisOfOtherComprehensiveIncomeItemsResultingFromHedgeAccountingExplanatory
654 Summary of Details of Hedged Exposures by Hedging Strategies Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailsOfHedgedExposuresByHedgingStrategiesExplanatory
655 1077 - Disclosure - Other Financial Assets At Fair Value Through Profit Or Loss (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatoryTables
656 Implied Table Table

*

*

 implied:Table
657 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
658 Summary of Other Financial Assets at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsDesignatedAtFairValueThroughProfitOrLossExplanatory
659 1078 - Disclosure - Loans and Advances to Customers (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfLoansAndAdvancesToCustomersExplanatoryTables
660 Implied Table Table

*

*

 implied:Table
661 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
662 Summary of Net Loans and Advances to Customers Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfNetLoansAndAdvancesToCustomersExplanatory
663 Summary of Movement in Impairment Loss Allowances Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMovementInImpairmentLossAllowancesOnLoansAndAdvancesToCustomersExplanatory
664 Summary of Finance Lease and Hire Purchase Contract Receivables Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfFinanceLeaseAndHirePurchaseContractReceivablesExplanatory
665 1079 - Disclosure - Securitisations and Covered Bonds (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSecuritisationsAndCoveredBondsExplanatoryTables
666 Implied Table Table

*

*

 implied:Table
667 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
668 Analysis of Securitisations and Covered Bonds Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAnalysisOfSecuritisationsAndCoveredBondsExplanatory
669 Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfIssuancesAndRedemptionsOfSecuritisationAndCoveredBondProgrammesExplanatory
670 1080 - Disclosure - Transfers of Financial Assets Not Qualifying for Derecognition (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialAssetsTransferredDuringPeriodWhichDoNotQualifyForDerecognitionExplanatoryTables
671 Implied Table Table

*

*

 implied:Table
672 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
673 Carrying Amount of Financial Assets that Did Not Qualify for Derecognition and their Associated Financial Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCarryingAmountOfFinancialAssetsThatDidNotQualifyForDerecognitionAndTheirAssociatedFinancialLiabilitiesExplanatory
674 1081 - Disclosure - Reverse Repurchase Agreements - Non Trading (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfReverseRepurchaseAgreementsNontradingExplanatoryTables
675 Statement [table] Table

*

*

 ck0001649373:StatementTable
676 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
677 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
678 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
679 Statement [LineItems] LineItems ck0001649373:StatementLineItems
680 Summary of Reverse Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRepurchaseAndReverseRepurchaseAgreementsExplanatory
681 1082 - Disclosure - Other Financial Assets At Amortised Cost (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherFinancialAssetsAtAmortisedCostExplanatoryTables
682 Implied Table Table

*

*

 implied:Table
683 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
684 Summary of Other Financial Assets at Amortised Cost Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailedInformationOfOtherFinancialAssetsAtAmortisedCostExplanatory
685 1083 - Disclosure - Financial Assets At Fair Value Through Other Comprehensive Income (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatoryTables
686 Implied Table Table

*

*

 implied:Table
687 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
688 Summary of Financial Assets at Fair Value Through Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailedInformationAboutFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatory
689 1084 - Disclosure - Financial Investments (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInvestmentsExplanatoryTables
690 Implied Table Table

*

*

 implied:Table
691 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
692 Summary of Financial Investments Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfSummaryOfFinancialInvestmentsExplanatory
693 1085 - Disclosure - Interests in Other Entities (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfInterestsInOtherEntitiesExplanatoryTables
694 Statement [table] Table

*

*

 ck0001649373:StatementTable
695 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
696 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
697 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
698 Statement [LineItems] LineItems ck0001649373:StatementLineItems
699 Schedule of Interests in Other Entities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailedInformationAboutInterestsInOtherEntitiesExplanatory
700 Schedule of Subsidiaries With Significant Non-Controlling Interests Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfSubsidiaryWithSignificantNonControllingInterestsExplanatory
701 Summary of Interest in Other Entities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesExplanatory
702 Summary of companys interests in subsidiaries Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestsInSubsidiariesExplanatory
703 1086 - Disclosure - Intangible Assets (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfIntangibleAssetsAndGoodwillExplanatoryTables
704 Implied Table Table

*

*

 implied:Table
705 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
706 Schedule of Goodwill Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGoodwillExplanatory
707 Schedule of Goodwill for Cash Generating Units Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesExplanatory
708 Schedule of Other Intangibles Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIntangibleAssetsExplanatory
709 1087 - Disclosure - Trading Liabilities (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialLiabilitiesHeldForTradingExplanatoryTables
710 Implied Table Table

*

*

 implied:Table
711 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
712 Schedule of Trading Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTradingLiabilitiesExplanatory
713 1088 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossExplanatoryTables
714 Implied Table Table

*

*

 implied:Table
715 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
716 Summary of Other Financial Liabilities at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitsOrLossExplanatory
717 1089 - Disclosure - Deposits by Customers (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDepositsFromCustomersExplanatoryTables
718 Implied Table Table

*

*

 implied:Table
719 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
720 Schedule of Deposits by Customers Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailedInformationAboutDepositsFromCustomersExplanatory
721 1090 - Disclosure - Deposits by Banks (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDepositsFromBanksExplanatoryTables
722 Implied Table Table

*

*

 implied:Table
723 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
724 Schedule of Deposits by Banks Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDepositsByBankExplanatory
725 1091 - Disclosure - Repurchase Agreements - Non Trading (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfRepurchaseAgreementsNontradingExplanatoryTables
726 Implied Table Table

*

*

 implied:Table
727 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
728 Summary of Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ck0001649373:DetailedDisclosureOfRepurchaseAgreementsNontradingExplanatory
729 1092 - Disclosure - Debt Securities in Issue (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfDebtSecuritiesExplanatoryTables
730 Implied Table Table

*

*

 implied:Table
731 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
732 Summary of Debt Securities in Issue Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDebtSecuritiesInIssueExplanatory
733 1093 - Disclosure - Subordinated Liabilities (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSubordinatedLiabilitiesExplanatoryTables
734 Statement [table] Table

*

*

 ck0001649373:StatementTable
735 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
736 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
737 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
738 Statement [LineItems] LineItems ck0001649373:StatementLineItems
739 Schedule of Subordinated Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDetailsOfSubordinatedLiabilitiesExplanatory
740 Summary of Undated Subordinated Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfUndatedSubordinatedLiabilitiesExplanatory
741 Summary of Dated Subordinated Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDatedSubordinatedLiabilitiesExplanatory
742 1094 - Disclosure - Provisions (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfProvisionsExplanatoryTables
743 Implied Table Table

*

*

 implied:Table
744 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
745 Summary of Provisions Reconciliation Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfProvisionsReconciliationByClassExplanatory
746 Summary of Key Drivers of PPI Provision Balance and Forecast Assumptions Used in Calculating Provision Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfKeyDriversOfPPIProvisionBalanceAndForecastAssumptionsUsedInCalculatingProvisionExplanatory
747 1095 - Disclosure - Retirement Benefit Plans (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfEmployeeBenefitsExplanatoryTables
748 Implied Table Table

*

*

 implied:Table
749 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
750 Summary of Retirement Benefit Plans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDefinedBenefitPlansExplanatory
751 Summary of Pension Remeasurement (Gains)/Losses Recognised In Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfPensionRemeasurementsIncludedInOtherComprehensiveIncomeExplanatory
752 Total defined benefit plan amount charged to the income statement Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTotalDefinedBenefitPlanAmountChargedToTheIncomeStatementExplanatory
753 Summary of Amounts Recognised in Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAmountsRecognisedInOtherComprehensiveIncomeExplanatory
754 Disclosure of Movements in Present Value of Defined Benefit Obligations Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMovementsInThePresentValueOfDefinedBenefitObligationsExplanatory
755 Disclosure of Movements in Fair Value of Schemes' Assets Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMovementsInFairValueOfSchemesAssetsExplanatory
756 Summary of Composition and Fair Value of Plan Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFairValueOfPlanAssetsExplanatory
757 Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDefinedBenefitPlanActuarialAssumptionsExplanatory
758 Summary of Actuarial Assumption Sensitivities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsExplanatory
759 Disclosure of Benefits Expected To Be Paid Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfDefinedBenefitPlanExpectedFutureBenefitPaymentsExplanatory
760 1096 - Disclosure - Contingent Liabilities And Commitments (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCommitmentsAndContingentLiabilitiesExplanatoryTables
761 Implied Table Table

*

*

 implied:Table
762 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
763 Summary of Contingent Liabilities and Commitments Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCommitmentsContingentLiabilitiesAndGuaranteesExplanatory
764 Operating Lease Commitments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfMaturityAnalysisOfOperatingLeasePaymentsExplanatory
765 1097 - Disclosure - Share Capital (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfIssuedCapitalExplanatoryTables
766 Implied Table Table

*

*

 implied:Table
767 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
768 Schedule of Share Capital Issued and Fully Paid Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfIssuedAndFullyPaidShareCapitalExplanatory
769 1098 - Disclosure - Other Equity Instruments (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherEquityInstrumentsExplanatoryTables
770 Implied Table Table

*

*

 implied:Table
771 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
772 Summary of other equity instruments Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfSummaryOfOtherEquityInstrumentsExplanatory
773 1099 - Disclosure - Non-Controlling Interests (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfNoncontrollingInterestsExplanatoryTables
774 Implied Table Table

*

*

 implied:Table
775 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
776 Schedule of Amounts Attributable to Non-Controlling Interests Concept (Text Block (HTML)) For Period ck0001649373:ScheduleOfInformationAboutAmountsAttributableToNonControllingInterestsExplanatory
777 1100 - Disclosure - Changes in Liabilities Arising from Financing Activities (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfReconciliationOfLiabilityArisingFromFinancingActivitiesExplanatoryTables
778 Statement [table] Table

*

*

 ck0001649373:StatementTable
779 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
780 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
781 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
782 Statement [LineItems] LineItems ck0001649373:StatementLineItems
783 Summary of Changes in Liabilities Arising from Financing Activities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesExplanatory
784 1101 - Disclosure - Assets Charged As Security For Liabilities And Collateral Accepted As Security For Assets (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfCollateralExplanatoryTables
785 Implied Table Table

*

*

 implied:Table
786 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
787 Financial Assets Charged as Security Under On-Balance Sheet and Off-Balance Concept (Text Block (HTML)) For Period ck0001649373:ScheduleOfFinancialAssetsChargedAsSecurityForLiabilitiesExplanatory
788 Schedule of Collateral Held as Security For Assets Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfCollateralAcceptedAsSecurityForAssetsExplanatory
789 1102 - Disclosure - Share-Based Compensation (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfSharebasedPaymentArrangementsExplanatoryTables
790 Statement [table] Table

*

*

 ck0001649373:StatementTable
791 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
792 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
793 2015 LTIP [member] Member ck0001649373:TwoThousandAndFifteenLongTermIncentivePlanMember
794 Statement [LineItems] LineItems ck0001649373:StatementLineItems
795 Summary of Movement in Share Options Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNumberAndWeightedAverageExercisePricesOfShareOptionsExplanatory
796 Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfRangeOfExercisePricesAndWeightedAverageRemainingContractualLifeOfOptionsOutstandingExplanatory
797 Summary of Movement in Value of Conditional Awards in LTIPs Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMovementInValueOfConditionalAwardsExplanatory
798 1103 - Disclosure - Transactions With Directors and Other Key Management Personnel (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfInformationAboutKeyManagementPersonnelExplanatoryTables
799 Implied Table Table

*

*

 implied:Table
800 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
801 Summary of Remuneration of the Directors and Other Key Management Personnel Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfRemunerationOfDirectorsAndOtherKeyManagementPersonnelExplanatory
802 Summary of Transactions with Directors, Other Key Management Personnel Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfTransactionsWithDirectorsKeyManagementPersonnelAndTheirConnectedPersonsExplanatory
803 1104 - Disclosure - Related Party Disclosures (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfRelatedPartyExplanatoryTables
804 Implied Table Table

*

*

 implied:Table
805 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
806 Summary of Transactions With Related Parties Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesExplanatory
807 1105 - Disclosure - Financial Instruments (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInstrumentsExplanatoryTables
808 Implied Table Table

*

*

 implied:Table
809 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
810 Fair Values of Financial Instruments Carried at Amortised Cost Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfFairValueOfFinancialInstrumentsAtAmortisedCostExplanatory
811 Fair Values of Financial Instruments Measured at Fair Value on a Recurring Basis Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfFairValueOfFinancialInstrumentsAtFairValueExplanatory
812 Summary of Fair Value Adjustment Concept (Text Block (HTML)) For Period ck0001649373:ScheduleOfFairValueAdjustmentExplanatory
813 Analysis of Financial Instruments Valued Using Internal Models Based on Information Other Than Market Data Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfAnalysisOfFinancialInstrumentsValuedUsingInternalModelsBasedOnInformationOtherThanMarketDataExplanatory
814 Reconciliation of Fair Value Measurements in Level 3 of the Fair Value Hierarchy Concept (Text Block (HTML)) For Period ck0001649373:ReconciliationOfFairValueMeasurementsInLevelThreeOfTheFairValueHierarchyExplanatory
815 Effects of Changes in Significant Unobservable Assumptions to Reasonably Possible Alternatives (Level 3) Concept (Text Block (HTML)) For Period ck0001649373:EffectsOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevelThreeExplanatory
816 Maturities of Undiscounted Cash Flows for Financial Liabilities and Off Balance Sheet Commitments Concept (Text Block (HTML)) For Period ck0001649373:MaturitiesOfUndiscountedCashFlowsForFinancialLiabilitiesAndOffBalanceSheetCommitmentsExplanatory
817 1106 - Disclosure - Offsetting Financial Assets and Liabilities (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfOffsettingOfFinancialAssetsAndFinancialLiabilitiesExplanatoryTables
818 Implied Table Table

*

*

 implied:Table
819 Text block [abstract] Abstract ck0001649373:TextBlockAbstract
820 Summary of Information about Impact of Offsetting of Financial Assets and Liabilities Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfOffsettingFinancialAssetsAndLiabilitiesExplanatory
821 1107 - Disclosure - Transition to IFRS 9 (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfImpactOfAdoptionOfIFRS9ExplanatoryTables
822 Statement [table] Table

*

*

 ck0001649373:StatementTable
823 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
824 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
825 IFRS 9 [member] Member ck0001649373:IFRS9Member
826 Statement [LineItems] LineItems ck0001649373:StatementLineItems
827 Summary of Measurement Categories and Carrying Amounts of Financial Assets Determined in Accordance with IAS 39 and IFRS 9 Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfMeasurementCategoriesAndCarryingAmountsOfFinancialAssetsExplanatory
828 Disclosure of Statutory Balance Sheet Reconciliation under IAS 39 and IFRS 9 Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsExplanatory
829 1108 - Disclosure - Loans and Advances to Banks (Tables) Network

*

*

 http://santander.co.uk/taxonomy/role/NotesToFinancialStatementsDisclosureOfLoansAndAdvancesToBanksExplanatoryTables
830 Statement [table] Table

*

*

 ck0001649373:StatementTable
831 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
832 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
833 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
834 Statement [LineItems] LineItems ck0001649373:StatementLineItems
835 Summary of Loans and Advances to Banks - Parent Concept (Text Block (HTML)) For Period ck0001649373:DisclosureOfSummaryOfLoansAndAdvancesToBanksExplanatory
836 1109 - Disclosure - Credit Risk - Summary of Exposures to Credit Risk in Business Segments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfExposuresToCreditRiskInBusinessSegments
837 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
838 Segments [axis] Axis ifrs-full:SegmentsAxis
839 Segments [member] Member ifrs-full:SegmentsMember
840 Retail banking [member] Member ck0001649373:RetailBankingMember
841 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
842 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
843 Corporate centre [member] Member ck0001649373:CorporateCentreMember
844 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
845 Risks [member] Member ifrs-full:TypesOfRisksMember
846 Credit risk [member] Member ifrs-full:CreditRiskMember
847 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
848 Description of exposure to risk in business segments Concept (Text/String) For Period ifrs-full:DescriptionOfExposureToRisk
849 1110 - Disclosure - Credit Risk - Summary of Key Metrics to Measure and Control Credit Risk (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfKeyMetricsToMeasureAndControlCreditRisk
850 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
851 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
852 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
853 Non performing loans [member] Member ck0001649373:NonPerformingLoansMember
854 Expected Loss [member] Member ck0001649373:ExpectedLossMember
855 Expected credit losses [member] Member ck0001649373:ExpectedCreditLossesMember
856 Stages 1, 2 and 3 [member] Member ck0001649373:Stages12And3Member
857 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
858 Risks [member] Member ifrs-full:TypesOfRisksMember
859 Credit risk [member] Member ifrs-full:CreditRiskMember
860 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
861 Metric Concept (Text/String) For Period ifrs-full:MethodsUsedToMeasureRisk
862 Description Concept (Text/String) For Period ifrs-full:DescriptionOfObjectivesPoliciesAndProcessesForManagingRisk
863 1111 - Disclosure - Credit Risk - Summary of Compound Annual Growth Rates Over 5 Year Forecast (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCompoundAnnualGrowthRatesOver5YearForecast
864 Disclosure of compound annual growth rates forecast [table] Table

*

*

 ck0001649373:DisclosureOfCompoundAnnualGrowthRatesForecastTable
865 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
866 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
867 Upside 2 [member] Member ck0001649373:UpsideTwoScenarioMember
868 Upside 1 [member] Member ck0001649373:UpsideOneScenarioMember
869 Base case [member] Member ck0001649373:BaseCaseScenarioMember
870 Downside 1 [member] Member ck0001649373:DownsideOneScenarioMember
871 Downside 2 [member] Member ck0001649373:DownsideTwoScenarioMember
872 Disclosure of forward looking information used in the determination of expected credit losses [line items] LineItems ck0001649373:DisclosureOfForwardLookingInformationUsedInTheDeterminationOfExpectedCreditLossesLineItems
873 House price index Concept (Percent) For Period ck0001649373:HousePriceIndexRate
874 GDP Concept (Percent) For Period ck0001649373:GrossDomesticProductRate
875 Unemployment rate Concept (Percent) For Period ck0001649373:UnemploymentRate
876 Interest rate Concept (Percent) For Period ck0001649373:InterestRate
877 1112 - Disclosure - Credit Risk - Summary of Probability Weightings Applied to Scenarios (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfProbabilityWeightingsAppliedToScenarios
878 Disclosure of probability weightings of scenarios [table] Table

*

*

 ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosTable
879 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
880 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
881 Upside 2 [member] Member ck0001649373:UpsideTwoScenarioMember
882 Upside 1 [member] Member ck0001649373:UpsideOneScenarioMember
883 Base case [member] Member ck0001649373:BaseCaseScenarioMember
884 Downside 1 [member] Member ck0001649373:DownsideOneScenarioMember
885 Downside 2 [member] Member ck0001649373:DownsideTwoScenarioMember
886 Disclosure of probability weightings of scenarios [line items] LineItems ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosLineItems
887 Probability % Concept (Percent) For Period ck0001649373:ProbabilityWeightingsOfScenarios
888 1113 - Disclosure - Credit Risk - Summary of Annual Growth Rates over 4 Year Forecast for CIB portfolio (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfAnnualGrowthRatesOver4YearForecastForCIBPortfolio
889 Disclosure of compound annual growth rates forecast [table] Table

*

*

 ck0001649373:DisclosureOfCompoundAnnualGrowthRatesForecastTable
890 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
891 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
892 Upside Scenario [member] Member ck0001649373:UpsideScenarioMember
893 Base case [member] Member ck0001649373:BaseCaseScenarioMember
894 Downside Scenario [member] Member ck0001649373:DownsideScenarioMember
895 Segments [axis] Axis ifrs-full:SegmentsAxis
896 Segments [member] Member ifrs-full:SegmentsMember
897 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
898 Disclosure of forward looking information used in the determination of expected credit losses [line items] LineItems ck0001649373:DisclosureOfForwardLookingInformationUsedInTheDeterminationOfExpectedCreditLossesLineItems
899 GDP Concept (Percent) For Period ck0001649373:GrossDomesticProductRate
900 1114 - Disclosure - Credit Risk - Summary of Probability Weightings Applied to Scenarios for CIB Portfolio (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfProbabilityWeightingsAppliedToScenariosForCIBPortfolio
901 Disclosure of probability weightings of scenarios [table] Table

*

*

 ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosTable
902 Segments [axis] Axis ifrs-full:SegmentsAxis
903 Segments [member] Member ifrs-full:SegmentsMember
904 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
905 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
906 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
907 Upside Scenario [member] Member ck0001649373:UpsideScenarioMember
908 Base case [member] Member ck0001649373:BaseCaseScenarioMember
909 Downside Scenario [member] Member ck0001649373:DownsideScenarioMember
910 Disclosure of probability weightings of scenarios [line items] LineItems ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosLineItems
911 Probability % Concept (Percent) For Period ck0001649373:ProbabilityWeightingsOfScenarios
912 1115 - Disclosure - Credit Risk - Disclosure of Quantitative Criteria of Credit Risk Exposure (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskDisclosureOfQuantitativeCriteriaOfCreditRiskExposure
913 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
914 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
915 Products and services [member] Member ifrs-full:ProductsAndServicesMember
916 Mortgages [member] Member ifrs-full:MortgagesMember
917 Consumer (auto) finance [member] Member ifrs-full:ConsumerLoansMember
918 Personal loans [member] Member ck0001649373:PersonalLoansMember
919 Credit cards [member] Member ck0001649373:CreditCardsMember
920 Overdrafts [member] Member ck0001649373:OverdraftsMember
921 Segments [axis] Axis ifrs-full:SegmentsAxis
922 Segments [member] Member ifrs-full:SegmentsMember
923 Retail banking [member] Member ck0001649373:RetailBankingMember
924 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
925 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
926 Probability of default [axis] Axis ifrs-full:ProbabilityOfDefaultAxis
927 Entity's total for probability of default [member] Member ifrs-full:EntitysTotalForProbabilityOfDefaultMember
928 Probability of default [member] Member ifrs-full:ProbabilityOfDefaultMember
929 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
930 Other unsecured loans Concept (Percent) For Period ck0001649373:PDThresholdForMeasuringSignificantIncreaseInCreditRisk
931 Corporate & Investment Banking Concept (Text/String) For Period ck0001649373:CriteriaMeasuringSignificantIncreaseInCreditRisk
932 1116 - Disclosure - Credit Risk - Disclosure of Qualitative Criteria of Credit Risk Exposure (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskDisclosureOfQualitativeCriteriaOfCreditRiskExposure
933 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
934 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
935 Products and services [member] Member ifrs-full:ProductsAndServicesMember
936 Mortgages [member] Member ifrs-full:MortgagesMember
937 Consumer (auto) finance [member] Member ifrs-full:ConsumerLoansMember
938 Personal loans [member] Member ck0001649373:PersonalLoansMember
939 Credit cards [member] Member ck0001649373:CreditCardsMember
940 Overdrafts [member] Member ck0001649373:OverdraftsMember
941 Segments [axis] Axis ifrs-full:SegmentsAxis
942 Segments [member] Member ifrs-full:SegmentsMember
943 Retail banking [member] Member ck0001649373:RetailBankingMember
944 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
945 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
946 Qualitative Criteria For Measuring SICR Concept (Text/String) For Period ck0001649373:QualitativeCriteriaForMeasuringSignificantIncreaseInCreditRisk
947 1117 - Disclosure - Credit Risk - Summary of Difference Between Maximum and Net Exposure to Credit Risk - IFRS 9 (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfDifferenceBetweenMaximumAndNetExposureToCreditRiskIFRS9
948 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
949 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
950 Assets [member] Member ifrs-full:ClassesOfAssetsMember
951 Financial assets at amortised cost [member] Member ifrs-full:FinancialAssetsAtAmortisedCostMember
952 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
953 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
954 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
955 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
956 Off-Balance Sheet [member] Member ck0001649373:OffBalanceSheetMember
957 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
958 Risks [member] Member ifrs-full:TypesOfRisksMember
959 Credit risk [member] Member ifrs-full:CreditRiskMember
960 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
961 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
962 Cash and balances at central banks [member] Member ck0001649373:CashAndBalancesAtCentralBanksMember
963 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
964 Loans and advances to banks [member] Member ck0001649373:LoansAndAdvancesToBanksMember
965 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
966 Other financial assets at amortised cost [member] Member ck0001649373:OtherFinancialAssetsAtAmortisedCostMember
967 Financial assets at FVOCI [member] Member ck0001649373:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeMember
968 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
969 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
970 Carrying amount [member] Member ifrs-full:CarryingAmountMember
971 Cost [member] Member ifrs-full:GrossCarryingAmountMember
972 Accumulated Impairment [member] Member ifrs-full:AccumulatedImpairmentMember
973 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
974 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
975 Advances secured on residential property [member] Member ck0001649373:AdvancesSecuredOnResidentialPropertyMember
976 Corporate loans [member] Member ifrs-full:CorporateLoansMember
977 Finance leases [member] Member ifrs-full:LeaseReceivablesMember
978 Other unsecured advances [member] Member ck0001649373:OtherUnsecuredLoansMember
979 Amounts due from fellow banco santander group subsidiaries and joint ventures [member] Member ck0001649373:AmountsDueFromSubsidiariesAndJointVenturesMember
980 Loans and receivables securities [member] Member ifrs-full:LoansAndReceivablesCategoryMember
981 Available-for-sale [member] Member ifrs-full:FinancialAssetsAvailableforsaleCategoryMember
982 Held-to-maturity debt securities [member] Member ifrs-full:HeldtomaturityInvestmentsCategoryMember
983 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
984 Maximum exposure to balance sheet Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
985 Collateral cash Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
986 Collateral non-cash Concept (Monetary) As Of Debit ifrs-full:NoncashAssetsPledgedAsCollateralForWhichTransfereeHasRightByContractOrCustomToSellOrRepledgeCollateral
987 Netting Concept (Monetary) As Of Debit ifrs-full:FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
988 Net exposure Concept (Monetary) As Of ifrs-full:CreditExposure
989 1118 - Disclosure - Credit Risk - Summary of Difference Between Maximum and Net Exposure to Credit Risk (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfDifferenceBetweenMaximumAndNetExposureToCreditRisk
990 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
991 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
992 Assets [member] Member ifrs-full:ClassesOfAssetsMember
993 Securities Repurchased Under Resale Agreements [member] Member ck0001649373:SecuritiesRepurchasedUnderResaleAgreementsMember
994 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
995 Cash Collateral [member] Member ck0001649373:CashCollateralMember
996 Short-term loans [member] Member ck0001649373:ShortTermLoansMember
997 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
998 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
999 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1000 Trading Assets [member] Member ck0001649373:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTradingMember
1001 Derivative Financial Instruments [member] Member ck0001649373:DerivativeFinancialAssetsMember
1002 Other financial assets at fair value through profit loss [member] Member ck0001649373:OtherFinancialAssetsAtFairValueThroughProfitLossMember
1003 Financial assets at fair value through profit loss [member] Member ck0001649373:FinancialAssetsAtFairValueThroughProfitLossMember
1004 Financial Assets Designated at Fair Value [member] Member ck0001649373:FinancialAssetsAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognitionMember
1005 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1006 Risks [member] Member ifrs-full:TypesOfRisksMember
1007 Credit risk [member] Member ifrs-full:CreditRiskMember
1008 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1009 Maximum exposure to balance sheet Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1010 Collateral cash Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
1011 Collateral non-cash Concept (Monetary) As Of Debit ifrs-full:NoncashAssetsPledgedAsCollateralForWhichTransfereeHasRightByContractOrCustomToSellOrRepledgeCollateral
1012 Netting Concept (Monetary) As Of Debit ifrs-full:FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
1013 Net exposure Concept (Monetary) As Of ifrs-full:CreditExposure
1014 1119 - Disclosure - Credit Risk - Summary of Credit Rating of Financial Assets Subject to Credit Risk (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCreditRatingOfFinancialAssetsSubjectToCreditRisk
1015 Disclosure of internal credit grades [table] Table

*

*

 ifrs-full:DisclosureOfInternalCreditExposuresTable
1016 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
1017 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
1018 Stage 1 [member] Member ck0001649373:StageOneMember
1019 Stage 2 [member] Member ck0001649373:StageTwoMember
1020 Stage 3 [member] Member ck0001649373:StageThreeMember
1021 Loans and receivables securities [member] Member ifrs-full:LoansAndReceivablesCategoryMember
1022 Available-for-sale [member] Member ifrs-full:FinancialAssetsAvailableforsaleCategoryMember
1023 Held-to-maturity debt securities [member] Member ifrs-full:HeldtomaturityInvestmentsCategoryMember
1024 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
1025 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
1026 Balance sheet exposures [member] Member ck0001649373:BalanceSheetExposuresMember
1027 Off-Balance Sheet [member] Member ck0001649373:OffBalanceSheetMember
1028 Advances secured on residential property [member] Member ck0001649373:AdvancesSecuredOnResidentialPropertyMember
1029 Corporate loans [member] Member ifrs-full:CorporateLoansMember
1030 Finance leases [member] Member ifrs-full:LeaseReceivablesMember
1031 Other unsecured advances [member] Member ck0001649373:OtherUnsecuredLoansMember
1032 Amounts due from fellow banco santander group subsidiaries and joint ventures [member] Member ck0001649373:AmountsDueFromSubsidiariesAndJointVenturesMember
1033 Internal credit grades [axis] Axis ifrs-full:InternalCreditGradesAxis
1034 Entity's total for internal credit grades [member] Member ifrs-full:EntitysTotalForInternalCreditGradesMember
1035 Internal grade 9 [member] Member ck0001649373:InternalGradeNineMember
1036 Internal grade 8 [member] Member ck0001649373:InternalGradeEightMember
1037 Internal grade 7 [member] Member ck0001649373:InternalGradeSevenMember
1038 Internal grade 6 [member] Member ck0001649373:InternalGradeSixMember
1039 Internal grade 5 [member] Member ck0001649373:InternalGradeFiveMember
1040 Internal grade 4 [member] Member ck0001649373:InternalGradeFourMember
1041 Internal grade 3 to 1 [member] Member ck0001649373:InternalGradeThreeToOneMember
1042 Other [member] Member ck0001649373:OtherInternalGradeMember
1043 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1044 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1045 Cash and balances at central banks [member] Member ck0001649373:CashAndBalancesAtCentralBanksMember
1046 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
1047 Loans and advances to banks [member] Member ck0001649373:LoansAndAdvancesToBanksCategoryMember
1048 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
1049 Other financial assets at amortised cost [member] Member ck0001649373:OtherFinancialAssetsAtAmortisedCostMember
1050 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
1051 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
1052 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
1053 Assets [member] Member ifrs-full:ClassesOfAssetsMember
1054 Financial assets at amortised cost [member] Member ifrs-full:FinancialAssetsAtAmortisedCostMember
1055 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1056 Risks [member] Member ifrs-full:TypesOfRisksMember
1057 Credit risk [member] Member ifrs-full:CreditRiskMember
1058 Disclosure of internal credit grades [line items] LineItems ifrs-full:DisclosureOfInternalCreditExposuresLineItems
1059 Loss allowance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1060 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1061 1120 - Disclosure - Credit Risk - Summary of Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCreditPerformance
1062 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1063 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1064 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1065 Mortgages [member] Member ifrs-full:MortgagesMember
1066 Corporate loans [member] Member ifrs-full:CorporateLoansMember
1067 Segments [axis] Axis ifrs-full:SegmentsAxis
1068 Segments [member] Member ifrs-full:SegmentsMember
1069 Retail banking [member] Member ck0001649373:RetailBankingMember
1070 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1071 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1072 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1073 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
1074 Assets [member] Member ifrs-full:ClassesOfAssetsMember
1075 Loans to Customers [member] Member ck0001649373:LoansToCustomersMember
1076 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1077 Customer loans Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1078 NPLs Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoans
1079 NPL ratio Concept (Percent) As Of ck0001649373:RatioOfNonPerformingLoans
1080 Gross write-offs Concept (Monetary) For Period Debit ck0001649373:GrossWriteoffs
1081 Loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1082 1121 - Disclosure - Credit Risk - Summary of IFRS 9 Credit Quality (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfIFRS9CreditQuality
1083 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1084 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1085 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1086 Stage 1 [member] Member ck0001649373:StageOneMember
1087 Stage 2 [member] Member ck0001649373:StageTwoMember
1088 Stage 3 [member] Member ck0001649373:StageThreeMember
1089 Credit risk exposure approach [axis] Axis ck0001649373:CreditRiskExposureApproachAxis
1090 Credit risk exposure approach [member] Member ck0001649373:CreditRiskExposureApproachMember
1091 Drawn exposures [member] Member ck0001649373:DrawnExposuresMember
1092 Off-Balance Sheet Exposures [member] Member ck0001649373:OffbalanceSheetExposuresMember
1093 Segments [axis] Axis ifrs-full:SegmentsAxis
1094 Segments [member] Member ifrs-full:SegmentsMember
1095 Retail banking [member] Member ck0001649373:RetailBankingMember
1096 Retail banking mortgages [member] Member ck0001649373:RetailBankingMortgagesMember
1097 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1098 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1099 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1100 Stage Two Decomposition [axis] Axis ck0001649373:StageTwoDecompositionAxis
1101 Stage Two Decomposition [member] Member ck0001649373:StageTwoDecompositionMember
1102 Stage two below or equal to thirty DPD [member] Member ck0001649373:StageTwoBelowOrEqualToThirtyDpdMember
1103 Stage 2, above 30 DPD [member] Member ck0001649373:StageTwoAboveThirtyDPDMember
1104 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1105 Total exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1106 Loss Impairment: On Balance Sheet ECL Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1107 Loss Impairment: Off Balance Sheet ECL Concept (Monetary) As Of Credit ifrs-full:Provisions
1108 Total ECL Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1109 Total coverage ratio Concept (Percent) As Of ck0001649373:CoverageRatio
1110 1122 - Disclosure - Credit Risk - Summary of IFRS 9 Credit Quality (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfIFRS9CreditQualityParenthetical
1111 Implied Table Table

*

*

 implied:Table
1112 Disclosure of credit risk exposure [abstract] Abstract ifrs-full:DisclosureOfCreditRiskExposureAbstract
1113 Average PD percentage Concept (Percent) For Period ck0001649373:AssetsInDefaultProbabilityOfDefault
1114 Retail mortgage offers in pipeline Concept (Monetary) For Period Debit ck0001649373:RetailMortgageOffersInPipeline
1115 1123 - Disclosure - Credit Risk - Summary of Stage 2 Decomposition (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfStage2Decomposition
1116 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1117 Stage Two Decomposition [axis] Axis ck0001649373:StageTwoDecompositionAxis
1118 Stage Two Decomposition [member] Member ck0001649373:StageTwoDecompositionMember
1119 Currently in Arrears [member] Member ck0001649373:StageTwoBelowThirtyDpdMember
1120 Deterioation in probability of default [member] Member ck0001649373:DeterioationInProbabilityOfDefaultMember
1121 Other [member] Member ck0001649373:OtherMember
1122 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1123 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1124 Stage 2 [member] Member ck0001649373:StageTwoMember
1125 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1126 Exposure Concept (Monetary) As Of ifrs-full:CreditExposure
1127 1124 - Disclosure - Credit Risk - Summary of Reconciliation of Exposures, ECL and Net Carrying Amounts (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfReconciliationOfExposuresECLAndNetCarryingAmounts
1128 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1129 Segments [axis] Axis ifrs-full:SegmentsAxis
1130 Segments [member] Member ifrs-full:SegmentsMember
1131 Retail banking [member] Member ck0001649373:RetailBankingMember
1132 Mortgages [member] Member ifrs-full:MortgagesMember
1133 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1134 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1135 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1136 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1137 Risks [member] Member ifrs-full:TypesOfRisksMember
1138 Drawn exposures [member] Member ck0001649373:DrawnExposuresMember
1139 Off-Balance Sheet Exposures [member] Member ck0001649373:OffbalanceSheetExposuresMember
1140 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1141 Total exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1142 Total ECL on drawn exposures Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1143 Total ECL on off-balance sheet exposures Concept (Monetary) As Of Credit ifrs-full:Provisions
1144 On-balance sheet net carrying amount Concept (Monetary) As Of Debit ck0001649373:NetCreditExposure
1145 Other items Concept (Monetary) For Period Debit ck0001649373:OtherReconcilingItems
1146 Adjusted net carrying amount Concept (Monetary) For Period Debit ck0001649373:AdjustedNetCarryingAmount
1147 Assets classified at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
1148 Non-financial assets Concept (Monetary) As Of Debit ck0001649373:NonFinancialAssets
1149 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
1150 1125 - Disclosure - Credit Risk - Summary of ECL Reconciliation (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfECLReconciliation
1151 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
1152 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
1153 Credit impairment of financial instruments [member] Member ifrs-full:CreditImpairmentOfFinancialInstrumentsMember
1154 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1155 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1156 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1157 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1158 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1159 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1160 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1161 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1162 Stage 1 [member] Member ck0001649373:StageOneMember
1163 Stage 2 [member] Member ck0001649373:StageTwoMember
1164 Stage 3 [member] Member ck0001649373:StageThreeMember
1165 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1166 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1167 Stage 1 ECL [member] Member ck0001649373:StageOneExpectedCreditLossMember
1168 Stage 2 ECL [member] Member ck0001649373:StageTwoExpectedCreditLossMember
1169 Stage 3 ECL [member] Member ck0001649373:StageThreeExpectedCreditLossMember
1170 Total exposure [member] Member ck0001649373:TotalExposureMember
1171 Expected credit loss [member] Member ck0001649373:ExpectedCreditLossMember
1172 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items] LineItems ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems
1173 Beginning balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1174 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1175 Change in economic scenarios Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseThroughChangesInEconomicInputs
1176 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1177 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1178 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1179 Transfer to 12-month ECL Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1180 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1181 Transfer of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1182 Net re-measurement of ECL arising from transfer of stage Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1183 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1184 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1185 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1186 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1187 Ending balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1188 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1189 Net movement in the year Concept (Monetary) As Of ck0001649373:IncreaseDecreaseInTotalExpectedCreditLosses
1190 Net movement in the year Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseInTotalFinancialAssets
1191 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ck0001649373:GrossImpairmentLossIncomeStatementCharge
1192 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001649373:FinancialAssetsPostWriteoffRecoveries
1193 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1194 1126 - Disclosure - Credit Risk - Summary of Country Risk Exposure (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCountryRiskExposure
1195 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1196 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1197 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1198 Eurozone Countries [member] Member ifrs-full:CountryOfDomicileMember
1199 All Other Countries [member] Member ifrs-full:ForeignCountriesMember
1200 All Countries Excluding Eurozone Countries [member] Member ck0001649373:AllCountriesExcludingEurozoneCountriesMember
1201 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
1202 Counterparties [member] Member ifrs-full:CounterpartiesMember
1203 Governments [member] Member ifrs-full:GovernmentMember
1204 Government Guaranteed [member] Member ck0001649373:GovernmentGuaranteedMember
1205 Banks [member] Member ck0001649373:BankMember
1206 Other Financial Institutions [member] Member ck0001649373:OtherFinancialInstitutionsMember
1207 Retail [member] Member ck0001649373:RetailMember
1208 Corporate counterparty [member] Member ck0001649373:CorporateCounterpartyMember
1209 Geographical [Axis] Axis srt:StatementGeographicalAxis
1210 Geographical [Domain] Member srt:SegmentGeographicalDomain
1211 Ireland [member] Member country:IE
1212 Italy [member] Member country:IT
1213 Spain (excl. Banco Santander) [member] Member country:ES
1214 Portugal [member] Member country:PT
1215 France [member] Member country:FR
1216 Germany [member] Member country:DE
1217 Luxembourg [member] Member country:LU
1218 Other [member] Member ck0001649373:OtherCountriesMember
1219 UK [member] Member country:GB
1220 US [member] Member country:US
1221 Japan [member] Member country:JP
1222 Switzerland [member] Member country:CH
1223 Denmark [member] Member country:DK
1224 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1225 Risk exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1226 1127 - Disclosure - Credit Risk - Summary of Country Risk Exposure (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCountryRiskExposureParenthetical
1227 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1228 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1229 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1230 Eurozone Countries [member] Member ck0001649373:EuroZoneCountriesMember
1231 Geographical [Axis] Axis srt:StatementGeographicalAxis
1232 Geographical [Domain] Member srt:SegmentGeographicalDomain
1233 Netherlands [member] Member country:NL
1234 Belgium [Member] Member country:BE
1235 Greece [member] Member country:GR
1236 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1237 Risk exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1238 1128 - Disclosure - Credit Risk - Summary of Balances with Other Banco Santander Companies (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfBalancesWithOtherBancoSantanderCompanies
1239 Disclosure of detailed information about financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
1240 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
1241 Counterparties [member] Member ifrs-full:CounterpartiesMember
1242 Banks [member] Member ck0001649373:BankMember
1243 Other Financial Institutions [member] Member ck0001649373:OtherFinancialInstitutionsMember
1244 Corporate counterparty [member] Member ck0001649373:CorporateCounterpartyMember
1245 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1246 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1247 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
1248 Geographical [Axis] Axis srt:StatementGeographicalAxis
1249 Geographical [Domain] Member srt:SegmentGeographicalDomain
1250 Spain (excl. Banco Santander) [member] Member country:ES
1251 UK [member] Member country:GB
1252 Other [member] Member ck0001649373:OtherCountriesMember
1253 Uruguay [member] Member country:UY
1254 Disclosure of detailed information about financial instruments [line items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
1255 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1256 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
1257 1129 - Disclosure - Credit Risk - Summary of Balances with Other Banco Santander Companies (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfBalancesWithOtherBancoSantanderCompaniesParenthetical
1258 Disclosure of detailed information about financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
1259 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1260 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1261 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
1262 Range [axis] Axis ifrs-full:RangeAxis
1263 Ranges [member] Member ifrs-full:RangesMember
1264 Top of Range [member] Member ifrs-full:TopOfRangeMember
1265 Disclosure of detailed information about financial instruments [line items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
1266 Financial liabilities allocated to other countries Concept (Monetary) For Period Credit ck0001649373:FinancialLiabilitiesAllocatedToOtherCountries
1267 1130 - Disclosure - Credit Risk - Summary of Types of Credit Risk Mitigation (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfTypesOfCreditRiskMitigation
1268 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1269 Segments [axis] Axis ifrs-full:SegmentsAxis
1270 Segments [member] Member ifrs-full:SegmentsMember
1271 Residential mortgages [member] Member ck0001649373:ResidentialMortgagesMember
1272 Business Banking [member] Member ck0001649373:BusinessBankingMember
1273 Consumer (auto) finance [member] Member ck0001649373:ConsumerFinanceMember
1274 Unsecured Lending [member] Member ck0001649373:UnsecuredLendingMember
1275 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1276 Types of credit risk mitigation, including collateral, across portfolios Concept (Text/String) For Period ck0001649373:CreditRiskMitigationDescription
1277 1131 - Disclosure - Credit Risk - Summary of ECL Reconciliation for Retail Segment (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfECLReconciliationForRetailSegment
1278 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
1279 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
1280 Credit impairment of financial instruments [member] Member ifrs-full:CreditImpairmentOfFinancialInstrumentsMember
1281 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1282 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1283 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1284 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1285 Stage 1 ECL [member] Member ck0001649373:StageOneExpectedCreditLossMember
1286 Stage 2 ECL [member] Member ck0001649373:StageTwoExpectedCreditLossMember
1287 Stage 3 ECL [member] Member ck0001649373:StageThreeExpectedCreditLossMember
1288 Total exposure [member] Member ck0001649373:TotalExposureMember
1289 Expected credit loss [member] Member ck0001649373:ExpectedCreditLossMember
1290 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1291 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1292 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1293 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1294 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1295 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1296 Stage 1 [member] Member ck0001649373:StageOneMember
1297 Stage 2 [member] Member ck0001649373:StageTwoMember
1298 Stage 3 [member] Member ck0001649373:StageThreeMember
1299 Segments [axis] Axis ifrs-full:SegmentsAxis
1300 Segments [member] Member ifrs-full:SegmentsMember
1301 Retail banking [member] Member ck0001649373:RetailBankingMember
1302 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items] LineItems ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems
1303 Beginning balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1304 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1305 Change in economic scenarios Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseThroughChangesInEconomicInputs
1306 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1307 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1308 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1309 Transfer to 12-monthECL Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1310 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1311 Transfers of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1312 Net remeasurement of ECL on stage transfer Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1313 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1314 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1315 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1316 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1317 Ending balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1318 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1319 Net movement in the year Concept (Monetary) As Of ck0001649373:IncreaseDecreaseInTotalExpectedCreditLosses
1320 Net movement in the year Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseInTotalFinancialAssets
1321 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ck0001649373:GrossImpairmentLossIncomeStatementCharge
1322 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001649373:FinancialAssetsPostWriteoffRecoveries
1323 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1324 1132 - Disclosure - Credit Risk - Summary of Residential Mortgages by Borrower Profile (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByBorrowerProfile
1325 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1326 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1327 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1328 First-Time Buyers [member] Member ck0001649373:FirstTimeBuyersMember
1329 Home Movers [member] Member ck0001649373:HomeMoversMember
1330 Remortgagers [member] Member ck0001649373:RemortgagersMember
1331 Buy-To-Let [member] Member ck0001649373:BuyToLetMember
1332 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1333 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1334 Stock [member] Member ck0001649373:StockMember
1335 New Business [member] Member ck0001649373:NewBusinessMember
1336 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1337 Risks [member] Member ifrs-full:TypesOfRisksMember
1338 Credit risk [member] Member ifrs-full:CreditRiskMember
1339 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1340 Residential mortgage loans Concept (Monetary) As Of Debit ck0001649373:ResidentialMortgageLoans
1341 Percentage of residential mortgage loans Concept (Percent) As Of ck0001649373:ResidentialMortgageLoansPercentage
1342 1133 - Disclosure - Credit Risk - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskAdditionalInformation
1343 Disclosure of internal credit grades [table] Table

*

*

 ifrs-full:DisclosureOfInternalCreditExposuresTable
1344 Range [axis] Axis ifrs-full:RangeAxis
1345 Ranges [member] Member ifrs-full:RangesMember
1346 Greater Than 2.0m [member] Member ck0001649373:RangeFiveMember
1347 Less Than 70% [member] Member ck0001649373:LessThanOrEqualToSeventyPercentageMember
1348 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1349 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1350 Internal Remortgages [member] Member ck0001649373:InternalRemortgagesMember
1351 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1352 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1353 Development Loans [member] Member ck0001649373:DevelopmentLoansMember
1354 Segments [axis] Axis ifrs-full:SegmentsAxis
1355 Segments [member] Member ifrs-full:SegmentsMember
1356 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1357 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstate1Member
1358 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1359 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1360 Mortgages [member] Member ifrs-full:MortgagesMember
1361 Pre Two Thousand Nine Loans [member] Member ck0001649373:PreTwoThousandNineLoansMember
1362 Corporate loans [member] Member ifrs-full:CorporateLoansMember
1363 Customer Loans [member] Member ck0001649373:CustomerLoansMember
1364 Legacy Portfolios in Run-Off [member] Member ck0001649373:LegacyPortfoliosInRunoffMember
1365 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1366 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1367 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1368 Non performing loans [member] Member ck0001649373:NonPerformingLoansMember
1369 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1370 Risks [member] Member ifrs-full:TypesOfRisksMember
1371 Credit risk [member] Member ifrs-full:CreditRiskMember
1372 Maturity [axis] Axis ifrs-full:MaturityAxis
1373 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
1374 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
1375 Disclosure of internal credit grades [line items] LineItems ifrs-full:DisclosureOfInternalCreditExposuresLineItems
1376 Internal remortgages Concept (Monetary) As Of Debit ck0001649373:ResidentialMortgageLoansNewBusiness
1377 Advances and flexible mortgage drawdowns Concept (Monetary) As Of Debit ck0001649373:AdvancesAndFlexibleMortgageDrawdowns
1378 Number of individual mortgage loans Concept (Integer) As Of ck0001649373:NumberOfResidentialMortgageLoans
1379 New business number of individual mortgage loans Concept (Integer) As Of ck0001649373:NumberOfResidentialMortgageLoansNewBusiness
1380 Parts of the loans in negative equity that were effectively uncollateralised Concept (Monetary) As Of Debit ck0001649373:UncollateralisedLoans
1381 Average consumer finance loan size Concept (Monetary) As Of Credit ck0001649373:AverageConsumerFinanceLoanSize
1382 Average unsecured loan Concept (Monetary) As Of Credit ck0001649373:AverageUnsecuredLoan
1383 Credit card balances Concept (Monetary) As Of Credit ck0001649373:CreditCardBalance
1384 Percenatage of reverse repos to exposure Concept (Percent) For Period ck0001649373:PercentageOfCollateralHeldForReverseReposToExposure
1385 Percentage of collateral held against impaired loans Concept (Percent) As Of ck0001649373:CollateralHeldAgainstImpairedLoansPercentage
1386 Collateral held against Credit impaired assets Concept (Monetary) As Of Debit ck0001649373:CollateralHeldAgainstLoanCreditimpairedAssets
1387 Credit impaired assets Concept (Monetary) As Of Debit ck0001649373:CreditimpairedAssets
1388 Number of clients Concept (Integer) As Of ck0001649373:NumberOfClients
1389 Rate of derivative exposure with client Concept (Percent) As Of ck0001649373:DerivativeExposureWithClientPercentage
1390 Weighted-average credit rating percent Concept (Percent) As Of ifrs-full:ExpectedCreditLossRate
1391 Cash collateral held against portfolio Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
1392 Loans written down Concept (Monetary) As Of Credit ck0001649373:LoansAndAdvancesToCustomersWrittenDown
1393 Loan percentage Concept (Percent) As Of ck0001649373:PercentageOfLendingToCorporates
1394 Loan percentage Concept (Percent) As Of ck0001649373:PercentageOfLendingToCustomers
1395 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1396 Percentage of loan to value Concept (Percent) As Of ck0001649373:PercentageOfLoanToValueStock
1397 Loan percentage Concept (Percent) For Period ck0001649373:PercentageOfLoansWithDevelopmentRiskInCommercialRealEstatePortfolio
1398 Average loan balance Concept (Monetary) For Period Credit ck0001649373:AverageLoans
1399 Loans and advances to customers with higher LTV ratio Concept (Monetary) As Of Debit ck0001649373:LoansAndAdvancesToCustomersWithHigherLoanToValueRatio
1400 Percentage of maximum acceptable LTV ratio Concept (Percent) For Period ck0001649373:PercentageOfAcceptableMaximumLoanToValueRatio
1401 Impairment loss allowance Concept (Monetary) As Of Debit ck0001649373:ImpairmentLossAllowances
1402 1134 - Disclosure - Credit Risk - Summary of Residential Mortgages by Interest Rate Profile (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByInterestRateProfile
1403 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1404 Types of interest rates [axis] Axis ifrs-full:TypesOfInterestRatesAxis
1405 Interest rate types [member] Member ifrs-full:InterestRateTypesMember
1406 Fixed Rate [member] Member ifrs-full:FixedInterestRateMember
1407 Variable Rate [member] Member ifrs-full:FloatingInterestRateMember
1408 Standard Variable Rate [member] Member ck0001649373:StandardVariableRateMember
1409 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1410 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1411 Stock [member] Member ck0001649373:StockMember
1412 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1413 Risks [member] Member ifrs-full:TypesOfRisksMember
1414 Credit risk [member] Member ifrs-full:CreditRiskMember
1415 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1416 Residential mortgage loans Concept (Monetary) As Of Debit ck0001649373:ResidentialMortgageLoans
1417 Percentage of residential mortgage loans Concept (Percent) As Of ck0001649373:ResidentialMortgageLoansPercentage
1418 1135 - Disclosure - Credit Risk - Summary of Residential Mortgages by Geographical Distribution (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByGeographicalDistribution
1419 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1420 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1421 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1422 London [member] Member ck0001649373:LondonMember
1423 Midlands and East Anglia [member] Member ck0001649373:MidlandsAndEastAngliaMember
1424 North UK [member] Member ck0001649373:NorthUKMember
1425 Northern Ireland [member] Member ck0001649373:NorthernIrelandMember
1426 Scotland [member] Member ck0001649373:ScotlandMember
1427 South East Excluding London [member] Member ck0001649373:SouthEastExcludingLondonMember
1428 South West and Wales and Other [member] Member ck0001649373:SouthWestAndWalesAndOtherMember
1429 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1430 Risks [member] Member ifrs-full:TypesOfRisksMember
1431 Credit risk [member] Member ifrs-full:CreditRiskMember
1432 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1433 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1434 Stock [member] Member ck0001649373:StockMember
1435 New Business [member] Member ck0001649373:NewBusinessMember
1436 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1437 Residential mortgage loans Concept (Monetary) As Of Debit ck0001649373:ResidentialMortgageLoans
1438 1136 - Disclosure - Credit Risk - Summary of Residential Mortgages by Average Loan Size for New Business (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByAverageLoanSizeForNewBusiness
1439 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1440 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1441 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1442 South East Including London [member] Member ck0001649373:SouthEastIncludingLondonMember
1443 Rest of UK [member] Member ck0001649373:RestOfUKMember
1444 UK [member] Member country:GB
1445 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1446 New business residential mortgage loans average size Concept (Monetary) As Of Debit ck0001649373:ResidentialMortgageLoansNewBusinessAverageSize
1447 1137 - Disclosure - Credit Risk - Summary of Residential Mortgages by Loan Size (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByLoanSize
1448 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1449 Range [axis] Axis ifrs-full:RangeAxis
1450 Ranges [member] Member ifrs-full:RangesMember
1451 Less Than 0.25m [member] Member ck0001649373:RangeOneMember
1452 0.25m-0.50m[member] Member ck0001649373:RangeTwoMember
1453 0.50m-1.0m [member] Member ck0001649373:RangeThreeMember
1454 1.0m-2.0m [member] Member ck0001649373:RangeFourMember
1455 Greater Than 2.0m [member] Member ck0001649373:RangeFiveMember
1456 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1457 Risks [member] Member ifrs-full:TypesOfRisksMember
1458 Credit risk [member] Member ifrs-full:CreditRiskMember
1459 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1460 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1461 South East Including London [member] Member ck0001649373:SouthEastIncludingLondonMember
1462 UK [member] Member country:GB
1463 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1464 Residential mortgage loans Concept (Monetary) As Of Debit ck0001649373:ResidentialMortgageLoans
1465 1138 - Disclosure - Credit Risk - Summary of Residential Mortgages by Loan to Value (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByLoanToValue
1466 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1467 Range [axis] Axis ifrs-full:RangeAxis
1468 Ranges [member] Member ifrs-full:RangesMember
1469 Up to 50% [member] Member ck0001649373:UpToFiftyPercentageMember
1470 50 - 75% [member] Member ck0001649373:FiftyToSeventyFivePercentageMember
1471 75 - 85% [member] Member ck0001649373:SeventyFiveToEightyFivePercentageMember
1472 85 - 100% [member] Member ck0001649373:EightyFiveToHundredPercentageMember
1473 Greater Than 100% [member] Member ck0001649373:GreaterThanHundredPercentageMember
1474 Simple Average [member] Member ck0001649373:SimpleAverageMember
1475 Valuation Weighted Average LTV [member] Member ck0001649373:ValuationWeightedAverageMember
1476 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1477 Risks [member] Member ifrs-full:TypesOfRisksMember
1478 Credit risk [member] Member ifrs-full:CreditRiskMember
1479 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1480 Percentage of loan to value, Stock Concept (Percent) As Of ck0001649373:PercentageOfLoanToValueResidentialMortgages
1481 Collateral value of residential properties, Stock Concept (Monetary) As Of Debit ck0001649373:CollateralValueOfResidentialProperties
1482 Percentage of loan to value, NPL stock Concept (Percent) As Of ck0001649373:PercentageOfLoanToValueResidentialMortgagesNPLStock
1483 Collateral value of residential properties, NPL stock Concept (Monetary) As Of Debit ck0001649373:CollateralValueOfResidentialPropertiesNPLStock
1484 Percentage of loan to value, New business Concept (Percent) As Of ck0001649373:PercentageOfLoanToValueResidentialMortgagesNewBusiness
1485 Collateral value of residential properties, New business Concept (Monetary) As Of Debit ck0001649373:CollateralValueOfResidentialPropertiesNewBusiness
1486 1139 - Disclosure - Credit Risk - Summary of Residential Mortgages by Loan to Value (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByLoanToValueParenthetical
1487 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1488 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1489 Risks [member] Member ifrs-full:TypesOfRisksMember
1490 Credit risk [member] Member ifrs-full:CreditRiskMember
1491 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1492 Collateral against loans in negative equity Concept (Monetary) As Of Debit ck0001649373:CollateralValueOfResidentialPropertiesInNegativeEquity
1493 1140 - Disclosure - Credit Risk - Summary of Residential Mortgages by Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByCreditPerformance
1494 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1495 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1496 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1497 Performing Loans [member] Member ck0001649373:PerformingLoansMember
1498 Early Arrear Loans [member] Member ck0001649373:EarlyArrearLoansMember
1499 Non Performing Loans by Arrears [member] Member ck0001649373:NonPerformingLoansByArrearsMember
1500 Non Performing Loans by Bankruptcy [member] Member ck0001649373:NonPerformingLoansByBankruptcyMember
1501 Non Performing Loans by Maturity Default [member] Member ck0001649373:NonPerformingLoansByMaturityDefaultMember
1502 Non-performing loans by forbearance [member] Member ck0001649373:NonPerformingLoansByForbearanceMember
1503 Non Performing Loans by Properties in Possession [member] Member ck0001649373:NonPerformingLoansByPropertiesInPossessionMember
1504 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1505 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1506 Stage 1 [member] Member ck0001649373:StageOneMember
1507 Stage 2 [member] Member ck0001649373:StageTwoMember
1508 Stage 3 [member] Member ck0001649373:StageThreeMember
1509 Segments [axis] Axis ifrs-full:SegmentsAxis
1510 Segments [member] Member ifrs-full:SegmentsMember
1511 Mortgages [member] Member ifrs-full:MortgagesMember
1512 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1513 Risks [member] Member ifrs-full:TypesOfRisksMember
1514 Credit risk [member] Member ifrs-full:CreditRiskMember
1515 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1516 Past due status [member] Member ifrs-full:PastDueStatusMember
1517 Later Than 1 Month and Not Later Than 2 Months [member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1518 Later Than 2 Months And Not Later Than 3 Months [member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1519 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1520 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1521 Non performing loans Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoans
1522 Impairment loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1523 Stage 2 ratio Concept (Percent) As Of ck0001649373:StageTwoRatio
1524 Stage 3 ratio Concept (Percent) As Of ck0001649373:StageThreeRatio
1525 Early arrears ratio Concept (Percent) As Of ck0001649373:LoansEarlyArrearsRatio
1526 NPL ratio Concept (Percent) As Of ck0001649373:RatioOfNonPerformingLoans
1527 1141 - Disclosure - Credit Risk - Summary of Residential Mortgages by Credit Performance (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByCreditPerformanceParenthetical
1528 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1529 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1530 Past due status [member] Member ifrs-full:PastDueStatusMember
1531 Later Than 1 day and Not Later Than 1 Month [member] Member ck0001649373:LaterThanOneDayAndNotLaterThanOneMonthMember
1532 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1533 Non performing loans Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoans
1534 1142 - Disclosure - Credit Risk - Summary of ECL Reconciliation (Residential Mortgages) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfECLReconciliationResidentialMortgages
1535 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
1536 Segments [axis] Axis ifrs-full:SegmentsAxis
1537 Segments [member] Member ifrs-full:SegmentsMember
1538 Residential mortgages [member] Member ck0001649373:ResidentialMortgagesMember
1539 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1540 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1541 Stage 1 ECL [member] Member ck0001649373:StageOneExpectedCreditLossMember
1542 Stage 2 ECL [member] Member ck0001649373:StageTwoExpectedCreditLossMember
1543 Stage 3 ECL [member] Member ck0001649373:StageThreeExpectedCreditLossMember
1544 Total exposure [member] Member ck0001649373:TotalExposureMember
1545 Expected credit loss [member] Member ck0001649373:ExpectedCreditLossMember
1546 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1547 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1548 Stage 1 [member] Member ck0001649373:StageOneMember
1549 Stage 2 [member] Member ck0001649373:StageTwoMember
1550 Stage 3 [member] Member ck0001649373:StageThreeMember
1551 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1552 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1553 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1554 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1555 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
1556 Credit impairment of financial instruments [member] Member ifrs-full:CreditImpairmentOfFinancialInstrumentsMember
1557 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1558 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1559 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items] LineItems ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems
1560 Beginning balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1561 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1562 Change in economic scenarios Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseThroughChangesInEconomicInputs
1563 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1564 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1565 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1566 Transfer to 12-monthECL Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1567 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1568 Transfers of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1569 Net remeasurement of ECL on stage transfer Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1570 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1571 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1572 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1573 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1574 Ending balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1575 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1576 Net movement in the year Concept (Monetary) As Of ck0001649373:IncreaseDecreaseInTotalExpectedCreditLosses
1577 Net movement in the year Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseInTotalFinancialAssets
1578 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ck0001649373:GrossImpairmentLossIncomeStatementCharge
1579 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001649373:FinancialAssetsPostWriteoffRecoveries
1580 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1581 1143 - Disclosure - Credit Risk - Summary of Modification of Loan Terms (Residential Mortgages) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfModificationOfLoanTermsResidentialMortgages
1582 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1583 Segments [axis] Axis ifrs-full:SegmentsAxis
1584 Segments [member] Member ifrs-full:SegmentsMember
1585 Mortgages [member] Member ifrs-full:MortgagesMember
1586 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1587 Amortised cost before modification Concept (Monetary) For Period Debit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesAmortisedCostBeforeModification
1588 Net modification loss Concept (Monetary) For Period Credit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesModificationGainLoss
1589 Gross carrying amount of financial assets for which the ECL allowance has changed to 12-month measurement during the year Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsWithModifiedContractualCashFlowsWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesForWhichLossAllowanceChangedDuringReportingPeriodTo12monthExpectedCreditLossesGrossCarryingAmount
1590 1144 - Disclosure - Credit Risk - Summary of Residential Mortgages by Forbearance Applied (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesByForbearanceApplied
1591 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1592 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1593 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1594 Stage 2 [member] Member ck0001649373:StageTwoMember
1595 Stage 3 [member] Member ck0001649373:StageThreeMember
1596 Forbearance in Arrears [member] Member ck0001649373:ForbearanceInArrearsMember
1597 Performing [member] Member ck0001649373:PerformingForbearanceMember
1598 Segments [axis] Axis ifrs-full:SegmentsAxis
1599 Segments [member] Member ifrs-full:SegmentsMember
1600 Mortgages [member] Member ifrs-full:MortgagesMember
1601 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1602 Capitalisation Concept (Monetary) As Of Debit ck0001649373:LoansCapitalisationForbearance
1603 Term extension Concept (Monetary) As Of Debit ck0001649373:LoansTermExtensionForbearance
1604 Interest-only Concept (Monetary) As Of Debit ck0001649373:LoansInterestOnlyForbearance
1605 Total Concept (Monetary) As Of Debit ck0001649373:LoansForbearance
1606 Impairment loss allowances Concept (Monetary) As Of Credit ck0001649373:AllowanceAccountForCreditLossesOfLoansForbearance
1607 Loans capitalisation forbearance Percentage Concept (Percent) As Of ck0001649373:LoansCapitalisationForbearancePercentage
1608 Loans term extension forbearance percentage Concept (Percent) As Of ck0001649373:LoansTermExtensionForbearancePercentage
1609 Loans interest only forbearance percentage Concept (Percent) As Of ck0001649373:LoansInterestOnlyForbearancePercentage
1610 Loans forbearance percentage Concept (Percent) As Of ck0001649373:LoansForbearancePercentage
1611 1145 - Disclosure - Credit Risk - Summary of Residential Mortgages Portfolios of Particular Interest by Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesPortfoliosOfParticularInterestByCreditPerformance
1612 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1613 Segments [axis] Axis ifrs-full:SegmentsAxis
1614 Segments [member] Member ifrs-full:SegmentsMember
1615 Mortgages [member] Member ifrs-full:MortgagesMember
1616 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1617 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1618 Stage 1 [member] Member ck0001649373:StageOneMember
1619 Stage 2 [member] Member ck0001649373:StageTwoMember
1620 Stage 3 [member] Member ck0001649373:StageThreeMember
1621 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1622 Past due status [member] Member ifrs-full:PastDueStatusMember
1623 Later Than 1 Month and Not Later Than 2 Months [member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1624 Later Than 2 Months And Not Later Than 3 Months [member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1625 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1626 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1627 Performing Loans [member] Member ck0001649373:PerformingLoansMember
1628 Early Arrear Loans [member] Member ck0001649373:EarlyArrearLoansMember
1629 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1630 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1631 Interest Only Loan [member] Member ck0001649373:InterestOnlyLoanMember
1632 Part Interest Only Part Repayment [member] Member ck0001649373:PartInterestOnlyPartRepaymentMember
1633 Flexible Interest Loan [member] Member ck0001649373:FlexibleInterestLoanMember
1634 Loan To Value Greater Than 100% Loan [member] Member ck0001649373:LoanToValueGreaterThanHundredPercentageLoanMember
1635 Buy To Let Loan [member] Member ck0001649373:BuyToLetLoanMember
1636 Other [member] Member ck0001649373:OtherPortfolioMember
1637 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1638 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1639 Stage 3 ratio Concept (Percent) As Of ck0001649373:StageThreeRatio
1640 NPLs Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoans
1641 NPL ratio Concept (Percent) As Of ck0001649373:RatioOfNonPerformingLoans
1642 PIPs Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoansByPropertiesInPossession
1643 1146 - Disclosure - Credit Risk - Summary of Residential Mortgages Portfolios of Particular Interest by Credit Performance (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesPortfoliosOfParticularInterestByCreditPerformanceParenthetical
1644 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1645 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1646 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1647 Part Interest Only Part Repayment [member] Member ck0001649373:PartInterestOnlyPartRepaymentMember
1648 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1649 Mortgage loan including interest-only part Concept (Monetary) As Of Debit ck0001649373:InterestOnlyPartOfPartInterestOnlyPartRepaymentProducts
1650 1147 - Disclosure - Credit Risk - Summary of Residential Mortgages Portfolios of Particular Interest by Forbearance Applied (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfResidentialMortgagesPortfoliosOfParticularInterestByForbearanceApplied
1651 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1652 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1653 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1654 Interest Only Loan [member] Member ck0001649373:InterestOnlyLoanMember
1655 Flexible Interest Loan [member] Member ck0001649373:FlexibleInterestLoanMember
1656 Loan To Value Greater Than 100% Loan [member] Member ck0001649373:LoanToValueGreaterThanHundredPercentageLoanMember
1657 Buy To Let Loan [member] Member ck0001649373:BuyToLetLoanMember
1658 Segments [axis] Axis ifrs-full:SegmentsAxis
1659 Segments [member] Member ifrs-full:SegmentsMember
1660 Mortgages [member] Member ifrs-full:MortgagesMember
1661 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1662 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1663 Stage 2 [member] Member ck0001649373:StageTwoMember
1664 Stage 3 [member] Member ck0001649373:StageThreeMember
1665 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1666 Total value Concept (Monetary) As Of Debit ck0001649373:LoansForbearance
1667 1148 - Disclosure - Credit Risk - Summary of Consumer (Auto) Finance and Other Unsecured Lending by Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfConsumerAutoFinanceAndOtherUnsecuredLendingByCreditPerformance
1668 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1669 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1670 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1671 Consumer (auto) finance [member] Member ifrs-full:ConsumerLoansMember
1672 Personal loans [member] Member ck0001649373:PersonalLoansMember
1673 Credit Card [member] Member ck0001649373:CreditCardMember
1674 Overdrafts [member] Member ck0001649373:OverdraftsMember
1675 Other unsecured advances [member] Member ck0001649373:OtherUnsecuredLoansMember
1676 Segments [axis] Axis ifrs-full:SegmentsAxis
1677 Segments [member] Member ifrs-full:SegmentsMember
1678 Consumer finance and unsecured lending [member] Member ck0001649373:ConsumerFinanceAndUnsecuredLendingMember
1679 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1680 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1681 Performing Loans [member] Member ck0001649373:PerformingLoansMember
1682 Early Arrear Loans [member] Member ck0001649373:EarlyArrearLoansMember
1683 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1684 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1685 Stage 1 [member] Member ck0001649373:StageOneMember
1686 Stage 2 [member] Member ck0001649373:StageTwoMember
1687 Stage 3 [member] Member ck0001649373:StageThreeMember
1688 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1689 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1690 NPL Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoans
1691 Loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1692 NPL ratio Concept (Percent) As Of ck0001649373:RatioOfNonPerformingLoans
1693 Stage 3 ratio Concept (Percent) As Of ck0001649373:StageThreeRatio
1694 Gross write-offs Concept (Monetary) For Period Debit ck0001649373:GrossWriteoffs
1695 1149 - Disclosure - Credit Risk - Summary of Modification of Loan Terms ( Consumer (Auto) Finance and Other Unsecured Lending) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfModificationOfLoanTermsConsumerAutoFinanceAndOtherUnsecuredLending
1696 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1697 Segments [axis] Axis ifrs-full:SegmentsAxis
1698 Segments [member] Member ifrs-full:SegmentsMember
1699 Consumer finance and unsecured lending [member] Member ck0001649373:ConsumerFinanceAndUnsecuredLendingMember
1700 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1701 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1702 Credit cards [member] Member ck0001649373:CreditCardsMember
1703 Overdrafts [member] Member ck0001649373:OverdraftsMember
1704 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1705 Amortised cost before modification Concept (Monetary) For Period Debit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesAmortisedCostBeforeModification
1706 Net modification loss Concept (Monetary) For Period Credit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesModificationGainLoss
1707 Gross carrying amount of financial assets for which the ECL allowance has changed to 12-month measurement during the year Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsWithModifiedContractualCashFlowsWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesForWhichLossAllowanceChangedDuringReportingPeriodTo12monthExpectedCreditLossesGrossCarryingAmount
1708 1150 - Disclosure - Credit Risk - Summary of Consumer (Auto) Finance and Other Unsecured Lending by Forbearance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfConsumerAutoFinanceAndOtherUnsecuredLendingByForbearance
1709 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1710 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1711 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1712 Personal loans [member] Member ck0001649373:PersonalLoansMember
1713 Credit cards [member] Member ck0001649373:CreditCardsMember
1714 Overdrafts [member] Member ck0001649373:OverdraftsMember
1715 Total other unsecured [member] Member ck0001649373:TotalOtherUnsecuredMember
1716 Segments [axis] Axis ifrs-full:SegmentsAxis
1717 Segments [member] Member ifrs-full:SegmentsMember
1718 Consumer finance and unsecured lending [member] Member ck0001649373:ConsumerFinanceAndUnsecuredLendingMember
1719 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1720 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1721 Stage 2 [member] Member ck0001649373:StageTwoMember
1722 Stage 3 [member] Member ck0001649373:StageThreeMember
1723 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1724 Forbearance Concept (Monetary) As Of Debit ck0001649373:LoansForbearance
1725 1151 - Disclosure - Credit Risk - Summary of Business Banking by Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfBusinessBankingByCreditPerformance
1726 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1727 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1728 Risks [member] Member ifrs-full:TypesOfRisksMember
1729 Credit risk [member] Member ifrs-full:CreditRiskMember
1730 Segments [axis] Axis ifrs-full:SegmentsAxis
1731 Segments [member] Member ifrs-full:SegmentsMember
1732 Business Banking [member] Member ck0001649373:BusinessBankingMember
1733 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1734 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1735 Stage 1 [member] Member ck0001649373:StageOneMember
1736 Stage 2 [member] Member ck0001649373:StageTwoMember
1737 Stage 3 [member] Member ck0001649373:StageThreeMember
1738 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1739 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1740 Performing Loans [member] Member ck0001649373:PerformingLoansMember
1741 Early Arrear Loans [member] Member ck0001649373:EarlyArrearLoansMember
1742 Non performing loans [member] Member ck0001649373:NonPerformingLoansMember
1743 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1744 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1745 Loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1746 Stage 3 ratio Concept (Percent) As Of ck0001649373:StageThreeRatio
1747 NPL ratio Concept (Percent) As Of ck0001649373:RatioOfNonPerformingLoans
1748 Gross write offs Concept (Monetary) For Period Debit ck0001649373:GrossWriteoffs
1749 1152 - Disclosure - Credit Risk - Summary of Modification of Loan Terms (Business Banking) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfModificationOfLoanTermsBusinessBanking
1750 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1751 Segments [axis] Axis ifrs-full:SegmentsAxis
1752 Segments [member] Member ifrs-full:SegmentsMember
1753 Business Banking [member] Member ck0001649373:BusinessBankingMember
1754 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1755 Amortised cost before modification Concept (Monetary) For Period Debit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesAmortisedCostBeforeModification
1756 Net modification loss Concept (Monetary) For Period Credit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesModificationGainLoss
1757 Gross carrying amount of financial assets for which the ECL allowance has changed to 12-month measurement during the year Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsWithModifiedContractualCashFlowsWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesForWhichLossAllowanceChangedDuringReportingPeriodTo12monthExpectedCreditLossesGrossCarryingAmount
1758 1153 - Disclosure - Credit Risk - Summary of Business Banking by Forbearance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfBusinessBankingByForbearance
1759 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1760 Segments [axis] Axis ifrs-full:SegmentsAxis
1761 Segments [member] Member ifrs-full:SegmentsMember
1762 Business Banking [member] Member ck0001649373:BusinessBankingMember
1763 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1764 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1765 Stage 2 [member] Member ck0001649373:StageTwoMember
1766 Stage 3 [member] Member ck0001649373:StageThreeMember
1767 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1768 Total value Concept (Monetary) As Of Debit ck0001649373:LoansForbearance
1769 1154 - Disclosure - Credit Risk - Summary of ECL Reconciliation For Other Business Segments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfECLReconciliationForOtherBusinessSegments
1770 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
1771 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
1772 Credit impairment of financial instruments [member] Member ifrs-full:CreditImpairmentOfFinancialInstrumentsMember
1773 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1774 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1775 Segments [axis] Axis ifrs-full:SegmentsAxis
1776 Segments [member] Member ifrs-full:SegmentsMember
1777 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1778 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1779 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1780 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1781 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1782 Stage 1 ECL [member] Member ck0001649373:StageOneExpectedCreditLossMember
1783 Stage 2 ECL [member] Member ck0001649373:StageTwoExpectedCreditLossMember
1784 Stage 3 ECL [member] Member ck0001649373:StageThreeExpectedCreditLossMember
1785 Total exposure [member] Member ck0001649373:TotalExposureMember
1786 Expected credit loss [member] Member ck0001649373:ExpectedCreditLossMember
1787 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1788 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1789 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1790 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1791 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1792 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1793 Stage 1 [member] Member ck0001649373:StageOneMember
1794 Stage 2 [member] Member ck0001649373:StageTwoMember
1795 Stage 3 [member] Member ck0001649373:StageThreeMember
1796 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items] LineItems ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems
1797 Beginning balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1798 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1799 Change in economic scenarios Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseThroughChangesInEconomicInputs
1800 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1801 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1802 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1803 Transfer to 12-month ECL Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1804 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1805 Transfers of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1806 Net remeasurement of ECL on stage transfer Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1807 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1808 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1809 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1810 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1811 Ending balance Concept (Monetary) As Of Credit ck0001649373:TotalExpectedCreditLosses
1812 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1813 Net movement in the year Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseInTotalFinancialAssets
1814 Net movement in the year Concept (Monetary) As Of ck0001649373:IncreaseDecreaseInTotalExpectedCreditLosses
1815 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ck0001649373:GrossImpairmentLossIncomeStatementCharge
1816 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001649373:FinancialAssetsPostWriteoffRecoveries
1817 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1818 1155 - Disclosure - Credit Risk - Summary of Other Segments Exposures by Credit Rating (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsExposuresByCreditRating
1819 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1820 Internal credit grades [axis] Axis ifrs-full:InternalCreditGradesAxis
1821 Entity's total for internal credit grades [member] Member ifrs-full:EntitysTotalForInternalCreditGradesMember
1822 Internal grade 9 [member] Member ck0001649373:InternalGradeNineMember
1823 Internal grade 8 [member] Member ck0001649373:InternalGradeEightMember
1824 Internal grade 7 [member] Member ck0001649373:InternalGradeSevenMember
1825 Internal grade 6 [member] Member ck0001649373:InternalGradeSixMember
1826 Internal grade 5 [member] Member ck0001649373:InternalGradeFiveMember
1827 Internal grade 4 [member] Member ck0001649373:InternalGradeFourMember
1828 Internal grade 3 to 1 [member] Member ck0001649373:InternalGradeThreeToOneMember
1829 Other [member] Member ck0001649373:OtherInternalGradeMember
1830 Segments [axis] Axis ifrs-full:SegmentsAxis
1831 Segments [member] Member ifrs-full:SegmentsMember
1832 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1833 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1834 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1835 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1836 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1837 SME and Mid Corporate [member] Member ck0001649373:SMEAndMidCorporateMember
1838 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstate1Member
1839 Social Housing [member] Member ck0001649373:SocialHousingMember
1840 Sovereign And Supranational [member] Member ck0001649373:SovereignAndSupranationalMember
1841 Large Corporate [member] Member ck0001649373:LargeCorporateMember
1842 Financial Institutions [member] Member ck0001649373:FinancialInstitutionsMember
1843 Structured Products [member] Member ck0001649373:StructuredProductsMember
1844 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
1845 Legacy Portfolios in Run-Off [member] Member ck0001649373:LegacyPortfoliosInRunoffMember
1846 Crown dependency branch [member] Member ck0001649373:CrownDependencyBranchMember
1847 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1848 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1849 Stage 1 [member] Member ck0001649373:StageOneMember
1850 Stage 2 [member] Member ck0001649373:StageTwoMember
1851 Stage 3 [member] Member ck0001649373:StageThreeMember
1852 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1853 Maximum exposure to credit risk Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1854 1156 - Disclosure - Credit Risk - Summary of Other Segments Exposures by Geographical Distribution (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsExposuresByGeographicalDistribution
1855 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1856 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1857 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1858 UK [member] Member country:GB
1859 Europe [member] Member ck0001649373:Europe1Member
1860 US [member] Member country:US
1861 Rest Of World [member] Member ck0001649373:RestOfWorldMember
1862 Segments [axis] Axis ifrs-full:SegmentsAxis
1863 Segments [member] Member ifrs-full:SegmentsMember
1864 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1865 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1866 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1867 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1868 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1869 SME and Mid Corporate [member] Member ck0001649373:SMEAndMidCorporateMember
1870 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstate1Member
1871 Social Housing [member] Member ck0001649373:SocialHousingMember
1872 Sovereign And Supranational [member] Member ck0001649373:SovereignAndSupranationalMember
1873 Large Corporate [member] Member ck0001649373:LargeCorporateMember
1874 Financial Institutions [member] Member ck0001649373:FinancialInstitutionsMember
1875 Structured Products [member] Member ck0001649373:StructuredProductsMember
1876 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
1877 Legacy Portfolios in Run-Off [member] Member ck0001649373:LegacyPortfoliosInRunoffMember
1878 Crown dependency branch [member] Member ck0001649373:CrownDependencyBranchMember
1879 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1880 Maximum exposure to credit risk Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1881 1157 - Disclosure - Credit Risk - Summary of Other Segments Exposures by Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsExposuresByCreditPerformance
1882 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1883 Segments [axis] Axis ifrs-full:SegmentsAxis
1884 Segments [member] Member ifrs-full:SegmentsMember
1885 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1886 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1887 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1888 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1889 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1890 SME and Mid Corporate [member] Member ck0001649373:SMEAndMidCorporateMember
1891 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstate1Member
1892 Social Housing [member] Member ck0001649373:SocialHousingMember
1893 Sovereign And Supranational [member] Member ck0001649373:SovereignAndSupranationalMember
1894 Large Corporate [member] Member ck0001649373:LargeCorporateMember
1895 Financial Institutions [member] Member ck0001649373:FinancialInstitutionsMember
1896 Structured Products [member] Member ck0001649373:StructuredProductsMember
1897 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
1898 Legacy Portfolios in Run-Off [member] Member ck0001649373:LegacyPortfoliosInRunoffMember
1899 Observed Impairment Loss Allowances [Member] Member ck0001649373:ObservedImpairmentLossAllowancesMember
1900 Allowance for IBNO [member] Member ck0001649373:AllowanceForIBNOMember
1901 Crown dependency branch [member] Member ck0001649373:CrownDependencyBranchMember
1902 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1903 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1904 Performing Exposure [member] Member ck0001649373:PerformingExposureMember
1905 Enhanced Monitoring [member] Member ck0001649373:EnhancedMonitoringMember
1906 Proactive Management [member] Member ck0001649373:ProactiveManagementMember
1907 Non-Performing Exposure [member] Member ck0001649373:NonperformingExposureMember
1908 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1909 Maximum exposure to credit risk Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1910 Observed impairment loss allowances Concept (Monetary) As Of Debit ck0001649373:AllowanceForObservedImpairmentLossesOnCreditExposure
1911 1158 - Disclosure - Credit Risk - Summary of Modification of Loan Terms (Other Segments Exposures) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfModificationOfLoanTermsOtherSegmentsExposures
1912 Disclosure of credit risk exposure [table] Table

*

*

 ifrs-full:DisclosureOfCreditRiskExposureTable
1913 Segments [axis] Axis ifrs-full:SegmentsAxis
1914 Segments [member] Member ifrs-full:SegmentsMember
1915 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1916 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1917 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1918 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1919 Amortised cost before modification Concept (Monetary) For Period Debit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesAmortisedCostBeforeModification
1920 Net modification loss Concept (Monetary) For Period Credit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesModificationGainLoss
1921 Gross carrying amount of financial assets for which the ECL allowance has changed to 12-month measurement during the year Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsWithModifiedContractualCashFlowsWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesForWhichLossAllowanceChangedDuringReportingPeriodTo12monthExpectedCreditLossesGrossCarryingAmount
1922 1159 - Disclosure - Credit Risk - Summary of Other Segments by Forbearance Applied (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsByForbearanceApplied
1923 Disclosure Of Forbearance [table] Table

*

*

 ck0001649373:DisclosureOfForbearanceTable
1924 Segments [axis] Axis ifrs-full:SegmentsAxis
1925 Segments [member] Member ifrs-full:SegmentsMember
1926 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
1927 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
1928 Corporate centre [member] Member ck0001649373:CorporateCentreMember
1929 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1930 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1931 Stage 1 [member] Member ck0001649373:StageOneMember
1932 Stage 2 [member] Member ck0001649373:StageTwoMember
1933 Stage 3 [member] Member ck0001649373:StageThreeMember
1934 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1935 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1936 Non-performing loans by forbearance [member] Member ck0001649373:NonPerformingLoansByForbearanceMember
1937 Performing [member] Member ck0001649373:PerformingForbearanceMember
1938 Disclosure Of Forbearance [line items] LineItems ck0001649373:DisclosureOfForbearanceLineItems
1939 - Term extension Concept (Monetary) As Of Debit ck0001649373:LoansTermExtensionForbearance
1940 - Interest-only Concept (Monetary) As Of Debit ck0001649373:LoansInterestOnlyForbearance
1941 - Other payment rescheduling Concept (Monetary) As Of Debit ck0001649373:LoansCapitalisationForbearance
1942 Loans forbearance Concept (Monetary) As Of Debit ck0001649373:LoansForbearance
1943 Proportion of portfolio Concept (Percent) As Of ck0001649373:LoansProportionOfPortfolioForbearancePercentage
1944 1160 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Credit Performance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCommercialRealEstateByCreditPerformance
1945 Disclosure of performance obligations [table] Table

*

*

 ifrs-full:DisclosureOfPerformanceObligationsTable
1946 Segments [axis] Axis ifrs-full:SegmentsAxis
1947 Segments [member] Member ifrs-full:SegmentsMember
1948 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstateSegmentMember
1949 Disclosure of performance obligations [line items] LineItems ifrs-full:DisclosureOfPerformanceObligationsLineItems
1950 Customer loans Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1951 NPLs Concept (Monetary) As Of Debit ck0001649373:NonPerformingLoans
1952 NPL ratio Concept (Percent) As Of ck0001649373:NonPerformingLoansRatio
1953 Gross write-offs Concept (Monetary) For Period Debit ck0001649373:GrossWriteoffs
1954 Impairment loss allowances Concept (Monetary) As Of Debit ck0001649373:ImpairmentLossAllowances
1955 1161 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Credit Performance (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCommercialRealEstateByCreditPerformanceParenthetical
1956 Disclosure of performance obligations [table] Table

*

*

 ifrs-full:DisclosureOfPerformanceObligationsTable
1957 Segments [axis] Axis ifrs-full:SegmentsAxis
1958 Segments [member] Member ifrs-full:SegmentsMember
1959 Retail Banking Segment [member] Member ck0001649373:RetailBankingSegmentMember
1960 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstateSegmentMember
1961 Disclosure of performance obligations [line items] LineItems ifrs-full:DisclosureOfPerformanceObligationsLineItems
1962 Consumer loans Concept (Monetary) As Of Debit ifrs-full:ConsumerLoans
1963 1162 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Loan to Value (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCommercialRealEstateByLoanToValue
1964 Disclosure Of Loan To Value [table] Table

*

*

 ck0001649373:DisclosureOfLoanToValueTable
1965 Segments [axis] Axis ifrs-full:SegmentsAxis
1966 Segments [member] Member ifrs-full:SegmentsMember
1967 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstate1Member
1968 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1969 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1970 Non performing loans [member] Member ck0001649373:NonPerformingLoansMember
1971 Range [axis] Axis ifrs-full:RangeAxis
1972 Ranges [member] Member ifrs-full:RangesMember
1973 Less Than Or Equal To Fifty Percentage [Member] Member ck0001649373:LessThanOrEqualToFiftyPercentageMember
1974 Greater than fifty percentage to seventy percentage [member] Member ck0001649373:GreaterThanFiftyPercentageToSeventyPercentageMember
1975 Greater Than 70-100% [member] Member ck0001649373:GreaterThanSeventyToHundredPercentageMember
1976 Greater Than 100% [member] Member ck0001649373:GreaterThanHundredPercentageMember
1977 Standardised Portfolio [member] Member ck0001649373:StandardizedPortfolioMember
1978 Total With Collateral [member] Member ck0001649373:CollateralMember
1979 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1980 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1981 Development Loans [member] Member ck0001649373:DevelopmentLoansMember
1982 Disclosure Of Loan To Value [line items] LineItems ck0001649373:DisclosureOfLoanToValueLineItems
1983 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1984 Percentage of loan to value Concept (Percent) As Of ck0001649373:PercentageOfLoanToValueStock
1985 1163 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Sector (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfCommercialRealEstateBySector
1986 Disclosure Of Loans And Advances By Industry Sector [table] Table

*

*

 ck0001649373:DisclosureOfLoansAndAdvancesByIndustrySectorTable
1987 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1988 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1989 Commercial Real Estate [member] Member ck0001649373:CommercialRealEstate1Member
1990 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
1991 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
1992 Office [member] Member ck0001649373:OfficeSectorMember
1993 Retail [member] Member ck0001649373:RetailMember
1994 Industrial [member] Member ck0001649373:IndustrialMember
1995 Residential [member] Member ck0001649373:ResidentialMember
1996 Mixed Use [member] Member ck0001649373:MixedUseMember
1997 Student Accommodation [member] Member ck0001649373:StudentLoansMember
1998 Hotels and Leisure [member] Member ck0001649373:HotelsAndLeisureMember
1999 Other [member] Member ck0001649373:OtherPortfolioMember
2000 Standardised Portfolio [member] Member ck0001649373:StandardizedPortfolioSectorMember
2001 Disclosure Of Loans And Advances By Industry Sector [line items] LineItems ck0001649373:DisclosureOfLoansAndAdvancesByIndustrySectorLineItems
2002 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
2003 Percentage of total CRE Portfolio Concept (Percent) As Of ck0001649373:PercentageOfCommercialRealEstatePortfolio
2004 1164 - Disclosure - Credit Risk - Summary of Social Housing Exposure (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditRiskSummaryOfSocialHousingExposure
2005 Disclosure Of Social Housing Exposure [table] Table

*

*

 ck0001649373:DisclosureOfSocialHousingExposureTable
2006 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2007 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2008 Social Housing [member] Member ck0001649373:SocialHousingMember
2009 Segments [axis] Axis ifrs-full:SegmentsAxis
2010 Segments [member] Member ifrs-full:SegmentsMember
2011 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
2012 Corporate centre [member] Member ck0001649373:CorporateCentreMember
2013 Disclosure Of Social Housing Exposure [line items] LineItems ck0001649373:DisclosureOfSocialHousingExposureLineItems
2014 Drawn Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
2015 Total Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
2016 1165 - Disclosure - Market Risk - Summary of Balance Sheet Allocation by Market Risk Classification (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureMarketRiskSummaryOfBalanceSheetAllocationByMarketRiskClassification
2017 Market Risk [table] Table

*

*

 ck0001649373:MarketRiskTable
2018 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2019 Risks [member] Member ifrs-full:TypesOfRisksMember
2020 Banking Market Risk [member] Member ck0001649373:BankingMarketRiskMember
2021 Trading Market Risk [member] Member ck0001649373:TradingMarketRiskMember
2022 Market Risk [member] Member ifrs-full:MarketRiskMember
2023 Market Risk [line items] LineItems ck0001649373:MarketRiskLineItems
2024 Cash and balances at central banks Concept (Monetary) As Of Debit ifrs-full:CashAndBankBalancesAtCentralBanks
2025 - Trading assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2026 - Derivative financial instruments Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
2027 - Other financial assets at FVTPL Concept (Monetary) As Of Debit ck0001649373:OtherFinancialAssetsAtFairValueThroughProfitOrLoss
2028 - Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
2029 - Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
2030 - Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ck0001649373:FinancialAssetsAtAmortisedCostReverseRepurchaseAgreementsNonTrading
2031 - Other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001649373:OtherFinancialAssetsAtAmortisedCost
2032 Financial assets at FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
2033 Financial investments Concept (Monetary) As Of Debit ck0001649373:FinancialInvestments
2034 Macro hedge of interest rate risk Concept (Monetary) As Of Debit ck0001649373:MacroHedgeOfInterestRateRisk
2035 Retirement benefit assets Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsDefinedBenefitPlan
2036 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
2037 - Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2038 - Derivative financial instruments Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
2039 - Other financial liabilities at FVTPL Concept (Monetary) As Of Credit ck0001649373:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
2040 - Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
2041 - Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2042 - Repurchase agreements - non trading Concept (Monetary) As Of Credit ck0001649373:FinancialLiabilitiesAtAmortisedCostRepurchaseAgreementsNonTrading
2043 - Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
2044 - Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
2045 Macro hedge of interest rate risk Concept (Monetary) As Of Credit ck0001649373:MacroHedgeOfInterestRateRiskLiability
2046 Retirement benefit obligations Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
2047 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
2048 1166 - Disclosure - Market Risk - Summary of Balance Sheet Allocation by Market Risk Classification (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureMarketRiskSummaryOfBalanceSheetAllocationByMarketRiskClassificationParenthetical
2049 Market Risk [table] Table

*

*

 ck0001649373:MarketRiskTable
2050 Classes of liabilities [axis] Axis ifrs-full:ClassesOfLiabilitiesAxis
2051 Liabilities [member] Member ifrs-full:LiabilitiesMember
2052 Other Liabilities [member] Member ck0001649373:OtherLiabilities1Member
2053 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
2054 Assets [member] Member ifrs-full:ClassesOfAssetsMember
2055 Other Assets [member] Member ifrs-full:OtherAssetsMember
2056 Market Risk [line items] LineItems ck0001649373:MarketRiskLineItems
2057 Macro hedge of interest rate risk including other assets Concept (Monetary) As Of Debit ck0001649373:MacroHedgeOfInterestRateRisk
2058 Macro hedge of interest rate risk including other liabilities Concept (Monetary) As Of Credit ck0001649373:MacroHedgeOfInterestRateRiskLiability
2059 1167 - Disclosure - Market Risk - Summary of NIM and EVE Sensitivity of Interest Rate Risk (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureMarketRiskSummaryOfNIMAndEVESensitivityOfInterestRateRisk
2060 Disclosure Of Sensitivity Limit Of Risk [table] Table

*

*

 ck0001649373:DisclosureOfSensitivityLimitOfRiskTable
2061 Range [axis] Axis ifrs-full:RangeAxis
2062 Ranges [member] Member ifrs-full:RangesMember
2063 +50bps [member] Member ck0001649373:IncreaseOfFiftyBasisPointsMember
2064 -50bps [member] Member ck0001649373:DecreaseOfFiftyBasisPointsMember
2065 Disclosure Of Sensitivity Limit Of Risk [line items] LineItems ck0001649373:DisclosureOfSensitivityLimitOfRiskLineItems
2066 NIM sensitivity Concept (Monetary) As Of Debit ck0001649373:NIMSensitivityRiskLimit
2067 EVE sensitivity (unaudited) Concept (Monetary) As Of Debit ck0001649373:EVESensitivityRiskLimit
2068 1168 - Disclosure - Market Risk - Summary of NIM and EVE Sensitivity of Interest Rate Risk (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureMarketRiskSummaryOfNIMAndEVESensitivityOfInterestRateRiskParenthetical
2069 Disclosure Of Sensitivity Limit Of Risk [table] Table

*

*

 ck0001649373:DisclosureOfSensitivityLimitOfRiskTable
2070 Range [axis] Axis ifrs-full:RangeAxis
2071 Ranges [member] Member ifrs-full:RangesMember
2072 +50bps [member] Member ck0001649373:IncreaseOfFiftyBasisPointsMember
2073 -50bps [member] Member ck0001649373:DecreaseOfFiftyBasisPointsMember
2074 Disclosure Of Sensitivity Limit Of Risk [line items] LineItems ck0001649373:DisclosureOfSensitivityLimitOfRiskLineItems
2075 Shift in basis point Concept (Percent) As Of ck0001649373:ShiftInBasisPoint
2076 1169 - Disclosure - Market Risk - Summary of Internal VaR for Exposure to Main Classes of Risk (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureMarketRiskSummaryOfInternalVaRForExposureToMainClassesOfRisk
2077 Market Risk [table] Table

*

*

 ck0001649373:MarketRiskTable
2078 Range [axis] Axis ifrs-full:RangeAxis
2079 Ranges [member] Member ifrs-full:RangesMember
2080 Weighted average [member] Member ifrs-full:WeightedAverageMember
2081 Top of Range [member] Member ifrs-full:TopOfRangeMember
2082 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2083 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2084 Risks [member] Member ifrs-full:TypesOfRisksMember
2085 Interest Rate Risks [member] Member ifrs-full:InterestRateRiskMember
2086 Equity Risks [member] Member ifrs-full:EquityPriceRiskMember
2087 Currency Risk [member] Member ifrs-full:CurrencyRiskMember
2088 Diversification Offsets [member] Member ifrs-full:RiskDiversificationEffectMember
2089 Market Risk [line items] LineItems ck0001649373:MarketRiskLineItems
2090 Risk exposure Concept (Monetary) As Of ifrs-full:ValueAtRisk
2091 1170 - Disclosure - Liquidity Risk - Summary of Reconciliation of Wholesale Funding to Balance Sheet (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLiquidityRiskSummaryOfReconciliationOfWholesaleFundingToBalanceSheet
2092 Reconciliation Of Wholesale Funding To Balance Sheet [table] Table

*

*

 ck0001649373:ReconciliationOfWholesaleFundingToBalanceSheetTable
2093 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2094 Risks [member] Member ifrs-full:TypesOfRisksMember
2095 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2096 Cash And Cash Equivalents 1 [axis] Axis ck0001649373:CashAndCashEquivalents1Axis
2097 Share-based Incentive Plans [member] Member ck0001649373:SharebasedIncentivePlansMember
2098 Wholesale Funding [member] Member ck0001649373:WholesaleFundingMember
2099 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2100 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2101 Deposits [member] Member ck0001649373:Deposits1Member
2102 Certificates of Deposit and Commercial Paper [member] Member ck0001649373:CertificatesOfDepositAndCommercialPaperMember
2103 Senior Unsecured - Public Benchmark [member] Member ck0001649373:SeniorUnsecuredPublicBenchmarkMember
2104 Senior Unsecured - Privately Placed [member] Member ck0001649373:SeniorUnsecuredPrivatelyPlacedMember
2105 Covered Bonds [member] Member ck0001649373:CoveredBondsMember
2106 Securitisation and Structured Issuance [member] Member ck0001649373:SecuritisationAndStructuredIssuanceMember
2107 Term Funding Scheme [member] Member ck0001649373:TermFundingSchemeMember
2108 Subordinated Liabilities and Equity [member] Member ck0001649373:SubordinatedLiabilitiesAndEquityMember
2109 Repurchase Agreement [member] Member ck0001649373:RepurchaseAgreementMember
2110 Foreign Exchange And Hedge Accounting [member] Member ck0001649373:ForeignExchangeAndHedgeAccountingMember
2111 Other Borrowing [Member] Member ck0001649373:OtherBorrowingMember
2112 Reconciliation Of Wholesale Funding To Balance Sheet [line items] LineItems ck0001649373:ReconciliationOfWholesaleFundingToBalanceSheetLineItems
2113 Funding analysis Concept (Monetary) As Of Credit ck0001649373:FundingAnalysis
2114 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2115 Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
2116 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
2117 Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2118 Financial liabilities at fair value Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
2119 Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
2120 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
2121 Other equity and non-controlling interests Concept (Monetary) As Of Credit ck0001649373:OtherEquityAndNoncontrollingInterests
2122 1171 - Disclosure - Liquidity Risk - Summary of Reconciliation of Wholesale Funding to Balance Sheet (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLiquidityRiskSummaryOfReconciliationOfWholesaleFundingToBalanceSheetParenthetical
2123 Reconciliation Of Wholesale Funding To Balance Sheet [table] Table

*

*

 ck0001649373:ReconciliationOfWholesaleFundingToBalanceSheetTable
2124 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
2125 Equity [member] Member ifrs-full:EquityMember
2126 Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001649373:NoncumulativeCallablePreferenceSharesMember
2127 Step-Up Callable Perpetual Reserve Capital Instruments [member] Member ck0001649373:StepupCallablePerpetualReserveCapitalInstrumentsMember
2128 Perpetual Capital Securities [member] Member ck0001649373:PerpetualCapitalSecuritiesMember
2129 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2130 Risks [member] Member ifrs-full:TypesOfRisksMember
2131 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2132 Reconciliation Of Wholesale Funding To Balance Sheet [line items] LineItems ck0001649373:ReconciliationOfWholesaleFundingToBalanceSheetLineItems
2133 Deposit from customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
2134 Other equity and non-controlling interests Concept (Monetary) As Of Credit ifrs-full:OtherEquityInterest
2135 1172 - Disclosure - Liquidity Risk - Summary of Sources of Wholesale Funding by Maturity (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLiquidityRiskSummaryOfSourcesOfWholesaleFundingByMaturity
2136 Disclosure of Sources of Wholesale Funding [table] Table

*

*

 ck0001649373:DisclosureOfSourcesOfWholesaleFundingTable
2137 Maturity [axis] Axis ifrs-full:MaturityAxis
2138 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2139 Not Later Than One Month [member] Member ifrs-full:NotLaterThanOneMonthMember
2140 Greater Than 1 and Less Than 3 Months [member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanThreeMonthsMember
2141 Greater Than 3 and Less Than 6 Months [member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanSixMonthsMember
2142 Greater Than 6 and Less Than 9 Months [member] Member ck0001649373:LaterThanSixMonthsAndNotLaterThanNineMonthsMember
2143 Greater Than 9 and Less Than 12 Months [member] Member ck0001649373:LaterThanNineMonthsAndNotLaterThanOneYearMember
2144 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2145 Later Than 1 Year and Not Later Than 2 Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
2146 Later Than 2 Year and Not Later Than 5 Years [member] Member ifrs-full:LaterThanTwoYearsAndNotLaterThanFiveYearsMember
2147 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
2148 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2149 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2150 Downstreamed From Santander UK Group Holdings Plc to Santander UK Plc [member] Member ck0001649373:DownstreamedFromSantanderUKGroupHoldingsPlcToSantanderUKPlcMember
2151 Other Santander UK Plc [member] Member ck0001649373:OtherSantanderUKPlcMember
2152 Other Group Entities [member] Member ck0001649373:OtherGroupEntitiesMember
2153 Disclosure of Maturity of Wholesale Funding [Line Items] LineItems ck0001649373:DisclosureOfSourcesOfWholesaleFundingLineItems
2154 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2155 Certificates of deposit and commercial paper Concept (Monetary) As Of Credit ck0001649373:CertificatesOfDepositAndCommercialPaper
2156 Senior unsecured - public benchmark Concept (Monetary) As Of Credit ck0001649373:SeniorUnsecuredPublicBenchmark
2157 Senior unsecured - privately placed Concept (Monetary) As Of Credit ck0001649373:SeniorUnsecuredPrivatelyPlaced
2158 Covered bonds Concept (Monetary) As Of Credit ck0001649373:CoveredBonds
2159 Subordinated liabilities and equity (incl. AT1) Concept (Monetary) As Of Credit ck0001649373:SubordinatedLiabilitiesAndEquity
2160 Securitisation and structured issuance Concept (Monetary) As Of Credit ck0001649373:SecuritisationAndStructuredIssuance
2161 Term Funding Scheme Concept (Monetary) As Of Credit ck0001649373:TermFundingScheme
2162 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
2163 Wholesale fund amount Concept (Monetary) As Of Credit ck0001649373:WholesaleFundAmount
2164 Of which: - secured Concept (Monetary) As Of Credit ck0001649373:SecuredWholesaleFundAmount
2165 Of which: - unsecured Concept (Monetary) As Of Credit ck0001649373:UnsecuredWholesaleFundAmount
2166 1173 - Disclosure - Liquidity Risk - Summary of Wholesale Funding by Currency (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLiquidityRiskSummaryOfWholesaleFundingByCurrency
2167 Currency Composition Of Wholesale Funds [table] Table

*

*

 ck0001649373:CurrencyCompositionOfWholesaleFundsTable
2168 Currency [Axis] Axis srt:CurrencyAxis
2169 All Currencies [Domain] Member currency:AllCurrenciesDomain
2170 United Kingdom, Pounds [member] Member currency:GBP
2171 United States of America, Dollars [member] Member currency:USD
2172 Euro Member Countries, Euro [member] Member currency:EUR
2173 Other [member] Member ck0001649373:OtherCurrenciesMember
2174 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2175 Risks [member] Member ifrs-full:TypesOfRisksMember
2176 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2177 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
2178 Counterparties [member] Member ifrs-full:CounterpartiesMember
2179 Santander UK Group Holdings Plc to Santander UK Plc [member] Member ck0001649373:SantanderUkGroupHoldingsPlcToSantanderUkPlcMember
2180 Santander UK Plc [member] Member ck0001649373:SantanderUkPlcMember
2181 Other Group Entities [member] Member ck0001649373:OtherGroupEntitiesMember
2182 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2183 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2184 Senior Unsecured - Public Benchmark [member] Member ck0001649373:SeniorUnsecuredPublicBenchmarkMember
2185 Senior Unsecured - Privately Placed [member] Member ck0001649373:SeniorUnsecuredPrivatelyPlacedMember
2186 Subordinated Liabilities and Equity [member] Member ck0001649373:SubordinatedLiabilitiesAndEquityMember
2187 Deposits by banks [member] Member ck0001649373:DepositsByBanksMember
2188 Certificates of Deposit and Commercial Paper [member] Member ck0001649373:CertificatesOfDepositAndCommercialPaperMember
2189 Covered Bonds [member] Member ck0001649373:CoveredBondsMember
2190 Securitisation and Structured Issuance [member] Member ck0001649373:SecuritisationAndStructuredIssuanceMember
2191 Term Funding Scheme [member] Member ck0001649373:TermFundingSchemeMember
2192 Subordinated liabilities [member] Member ck0001649373:SubordinatedLiabilitiesMember
2193 Currency Composition Of Wholesale Funds [line items] LineItems ck0001649373:CurrencyCompositionOfWholesaleFundsLineItems
2194 Percentage of wholesale funding by major currencies Concept (Percent) As Of ck0001649373:PercentageOfWholesaleFundingByCurrencies
2195 1174 - Disclosure - Liquidity Risk - Summary of External Term Issuance (Sterling Equivalent) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLiquidityRiskSummaryOfExternalTermIssuanceSterlingEquivalent
2196 Disclosure of detailed information about borrowings [table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
2197 Currency [Axis] Axis srt:CurrencyAxis
2198 All Currencies [Domain] Member currency:AllCurrenciesDomain
2199 United Kingdom, Pounds [member] Member currency:GBP
2200 United States of America, Dollars [member] Member currency:USD
2201 Euro Member Countries, Euro [member] Member currency:EUR
2202 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2203 Risks [member] Member ifrs-full:TypesOfRisksMember
2204 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2205 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
2206 Counterparties [member] Member ifrs-full:CounterpartiesMember
2207 Santander UK Group Holdings Plc to Santander UK Plc [member] Member ck0001649373:SantanderUkGroupHoldingsPlcToSantanderUkPlcMember
2208 Santander UK Plc [member] Member ck0001649373:SantanderUkPlcMember
2209 Other Group Entities [member] Member ck0001649373:OtherGroupEntitiesMember
2210 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2211 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2212 Senior Unsecured - Public Benchmark [member] Member ck0001649373:SeniorUnsecuredPublicBenchmarkMember
2213 Senior Unsecured - Privately Placed [member] Member ck0001649373:SeniorUnsecuredPrivatelyPlacedMember
2214 Subordinated Liabilities and Equity [member] Member ck0001649373:SubordinatedLiabilitiesAndEquityMember
2215 Securitisations [member] Member ifrs-full:SecuritisationsMember
2216 Covered Bonds [member] Member ck0001649373:CoveredBondsMember
2217 Term Funding Scheme [member] Member ck0001649373:TermFundingSchemeMember
2218 Disclosure of detailed information about borrowings [line items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
2219 Borrowings Concept (Monetary) As Of Credit ifrs-full:Borrowings
2220 1175 - Disclosure - Liquidity Risk - Summary of Loan-to-Deposit Ratio (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLiquidityRiskSummaryOfLoantoDepositRatio
2221 Disclosure of Customer Loans, Customer Deposits and Loan to Deposit Ratio [table] Table

*

*

 ck0001649373:DisclosureOfCustomerLoansCustomerDepositsAndLoanToDepositRatioTable
2222 Segments [axis] Axis ifrs-full:SegmentsAxis
2223 Segments [member] Member ifrs-full:SegmentsMember
2224 Retail banking [member] Member ck0001649373:RetailBankingMember
2225 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
2226 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
2227 Corporate centre [member] Member ck0001649373:CorporateCentreMember
2228 Disclosure of Customer Loans, Customer Deposits and Loan to Deposit Ratio [line items] LineItems ck0001649373:DisclosureOfCustomerLoansCustomerDepositsAndLoanToDepositRatioLineItems
2229 Consumer loans gross Concept (Monetary) As Of Debit ck0001649373:CustomerLoansGross
2230 Adjust for: fair value loans, impairment loss allowances, accrued interest and other Concept (Monetary) For Period Debit ck0001649373:AdjustForFairValueLoansImpairmentLossAllowancesAccruedInterestAndOtherCustomerLoans
2231 Statutory loans and advances to customers/deposits by customers Concept (Monetary) As Of Debit ck0001649373:StatutoryLoansAndAdvancesToCustomers
2232 Total Concept (Monetary) As Of Debit ck0001649373:CustomersLoansNet
2233 Deposits from customers gross Concept (Monetary) As Of Credit ck0001649373:CustomerDepositsGross
2234 Adjust for: fair value loans, impairment loss allowances, accrued interest and other Concept (Monetary) For Period Credit ck0001649373:AdjustForFairValueLoansImpairmentLossAllowancesAccruedInterestAndOtherDepositsFromCustomers
2235 Statutory loans and advances to customers/deposits by customers Concept (Monetary) As Of Credit ck0001649373:StatutoryDepositsByCustomers
2236 Total Concept (Monetary) As Of Credit ck0001649373:CustomersDepositsNet
2237 Percentage of loan to deposit ratio Concept (Percent) As Of ck0001649373:PercentageOfLoanToDepositRatio
2238 1176 - Disclosure - Capital Risk - Summary of Regulatory Capital Resources (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCapitalRiskSummaryOfRegulatoryCapitalResources
2239 Disclosure Of Regulatory Capital Resources [table] Table

*

*

 ck0001649373:DisclosureOfRegulatoryCapitalResourcesTable
2240 Components Of Regulatory Capital [axis] Axis ck0001649373:ComponentsOfRegulatoryCapitalAxis
2241 Components Of Regulatory Capital [member] Member ck0001649373:ComponentsOfRegulatoryCapitalMember
2242 Capital Instruments [member] Member ck0001649373:CapitalInstrumentsMember
2243 Retained Earnings [member] Member ifrs-full:RetainedEarningsMember
2244 Accumulated Other Reserves And Non-Controlling Interests [member] Member ck0001649373:AccumulatedOtherReservesAndNoncontrollingInterestsMember
2245 Amount of Qualifying Items Subject to Phase Out From AT1 [member] Member ck0001649373:PhaseOutFromAdditionalTierOneMember
2246 Tier Two Capital [member] Member ck0001649373:TierTwoCapitalMember
2247 Adjustments To Regulatory Capital [axis] Axis ck0001649373:AdjustmentsToRegulatoryCapitalAxis
2248 Adjustments To Regulatory Capital [member] Member ck0001649373:AdjustmentsToRegulatoryCapitalMember
2249 Capital before regulatory adjustments [member] Member ck0001649373:CapitalBeforeRegulatoryAdjustmentsMember
2250 Additional Value Adjustments [member] Member ck0001649373:AdditionalValueAdjustmentsMember
2251 Goodwill (Net of Tax) [member] Member ck0001649373:GoodwillNetOfTaxMember
2252 Other Intangibles [member] Member ifrs-full:OtherIntangibleAssetsMember
2253 Fair Value Reserves Related to Gains or Losses on Cash Flow Hedges [Member] Member ck0001649373:FairValueReserveMember
2254 Negative Amounts Resulting From the Calculation of Regulatory Expected Loss Amounts [member] Member ck0001649373:RegulatoryExpectedLossMember
2255 Gains or Losses on Liabilities Valued at Fair Value Resulting From Changes in Own Credit Standing [member] Member ck0001649373:ChangesInOwnCreditStandingMember
2256 Deferred Tax Assets That Rely on Future Profitability Excluding Timing Differences [member] Member ck0001649373:DeferredTaxAssetMember
2257 Defined Benefit Pension Fund Assets [member] Member ck0001649373:DefinedBenefitPensionFundAssetsMember
2258 Dividend Accrual [member] Member ck0001649373:DividendAccrualMember
2259 IFRS 9 Transitional Adjustment [member] Member ck0001649373:IFRS9TransitionalAdjustmentMember
2260 Non-Controlling Interests [member] Member ifrs-full:NoncontrollingInterestsMember
2261 Regulatory Deductions for Instruments Issued by Subsidiary Undertakings or Subject to CRDIV Amortisation [member] Member ck0001649373:InstrumentsIssuedBySubsidiaryMember
2262 Amount of qualifying items subject to phase out from Tier 2 [member] Member ck0001649373:PhaseOutFromAdditionalTierTwoMember
2263 Disclosure of Regulatory Capital Resources [Line Items] LineItems ck0001649373:DisclosureOfRegulatoryCapitalResourcesLineItems
2264 CET1 capital Concept (Monetary) As Of Credit ck0001649373:CommonEquityTierOneCapitalAmount
2265 AT1 capital Concept (Monetary) As Of Credit ck0001649373:AdditionalTierOneCapital
2266 Tier 1 capital Concept (Monetary) As Of Credit ck0001649373:TierOneCapitalAmount
2267 Tier 2 capital Concept (Monetary) As Of Credit ck0001649373:TierTwoCapital
2268 Total regulatory capital Concept (Monetary) As Of Debit ck0001649373:RegulatoryCapital
2269 1177 - Disclosure - Accounting Policies - Additional information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAccountingPoliciesAdditionalInformation
2270 Disclosure of changes in accounting estimates [table] Table

*

*

 ifrs-full:DisclosureOfChangesInAccountingEstimatesTable
2271 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
2272 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
2273 IFRS 9 [member] Member ck0001649373:IFRS9Member
2274 IFRS 16 [member] Member ck0001649373:IFRS16Member
2275 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2276 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2277 Stage 2 [member] Member ck0001649373:StageTwoMember
2278 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
2279 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
2280 House price index [Member] Member ck0001649373:HousePriceIndexMember
2281 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
2282 Past due status [member] Member ifrs-full:PastDueStatusMember
2283 180 Days [member] Member ck0001649373:OneHundredAndEightyDaysMember
2284 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2285 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2286 Unsecured Debt [member] Member ck0001649373:UnsecuredDebt1Member
2287 Amounts arising from insurance contracts [axis] Axis ifrs-full:AmountsArisingFromInsuranceContractsAxis
2288 Net amount arising from insurance contracts [member] Member ifrs-full:NetAmountArisingFromInsuranceContractsMember
2289 Payment protection insurance [member] Member ck0001649373:PaymentProtectionInsuranceMember
2290 Segments [axis] Axis ifrs-full:SegmentsAxis
2291 Segments [member] Member ifrs-full:SegmentsMember
2292 Retail banking Corporate and Commercial Banking and Corporate Centre [member] Member ck0001649373:RetailBankingCorporateAndCommercialBankingAndCorporateCentreMember
2293 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
2294 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
2295 Other provisions [member] Member ifrs-full:OtherProvisionsMember
2296 Miscellaneous other provisions [member] Member ifrs-full:MiscellaneousOtherProvisionsMember
2297 Disclosure of changes in accounting estimates [line items] LineItems ifrs-full:DisclosureOfChangesInAccountingEstimatesLineItems
2298 Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
2299 Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
2300 Deposit by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2301 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
2302 Increase Property, plant and equipment Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreasePropertyPlantAndEquipment
2303 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
2304 Other liabilities Concept (Monetary) As Of Credit ifrs-full:OtherLiabilities
2305 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
2306 Written off period for past due Concept (xbrli:durationItemType) For Period ck0001649373:WrittenOffPeriodForPastDue
2307 Expected credit losses allowance Concept (Monetary) For Period Credit ck0001649373:ExpectedCreditLossesAllowance
2308 Probability weight Concept (Percent) For Period ck0001649373:ProbabilityWeightedAverageOfExpectedCreditLosses
2309 Expected credit losses allowance for residential mortgages Concept (Monetary) For Period Credit ck0001649373:ExpectedCreditLossesAllowanceForResidentialMortgages
2310 Additional provisions Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
2311 Additional operational risk losses and restructuring charges Concept (Monetary) For Period Credit ck0001649373:AdditionalProvisionsOtherProvisionsOperationalRiskLossesAndRestructuringCharges
2312 Defined benefit pension schemes in net asset having surplus Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsDefinedBenefitPlan
2313 Defined benefit pension schemes in net liabilities having deficit Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
2314 1178 - Disclosure - Accounting Policies - Summary of Useful Lives or Depreciation Rates Used for Property, Plant and Equipment (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAccountingPoliciesSummaryOfUsefulLivesOrDepreciationRatesUsedForPropertyPlantAndEquipment
2315 Disclosure of detailed information about property, plant and equipment [table] Table

*

*

 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
2316 Range [axis] Axis ifrs-full:RangeAxis
2317 Ranges [member] Member ifrs-full:RangesMember
2318 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2319 Top of Range [member] Member ifrs-full:TopOfRangeMember
2320 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
2321 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
2322 Owner-occupied properties [member] Member ck0001649373:OwnerOccupiedPropertiesMember
2323 Office Fixtures and Equipment [member] Member ck0001649373:OfficeFixturesAndEquipmentMember
2324 Computer Software [member] Member ifrs-full:ComputerSoftwareMember
2325 Disclosure of detailed information about property, plant and equipment [line items] LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
2326 Useful lives or depreciation rates, property, plant and equipment Concept (xbrli:durationItemType) For Period ck0001649373:UsefulLivesPropertyPlantAndEquipment
2327 1179 - Disclosure - Accounting Policies - Summary of Probability Weights Applied for Each Scenario of Expected Credit Losses Allowance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAccountingPoliciesSummaryOfProbabilityWeightsAppliedForEachScenarioOfExpectedCreditLossesAllowance
2328 Disclosure of probability weightings of scenarios [table] Table

*

*

 ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosTable
2329 Project by scenario [axis] Axis ck0001649373:ProjectByScenarioAxis
2330 Project by scenario [member] Member ck0001649373:ProjectByScenarioMember
2331 Upside 2 [member] Member ck0001649373:UpsideTwoScenarioMember
2332 Upside 1 [member] Member ck0001649373:UpsideOneScenarioMember
2333 Base case [member] Member ck0001649373:BaseCaseScenarioMember
2334 Downside 1 [member] Member ck0001649373:DownsideOneScenarioMember
2335 Downside 2 [member] Member ck0001649373:DownsideTwoScenarioMember
2336 Downside [member] Member ck0001649373:DownsideMember
2337 Upside [member] Member ck0001649373:UpsideMember
2338 Segments [axis] Axis ifrs-full:SegmentsAxis
2339 Segments [member] Member ifrs-full:SegmentsMember
2340 Retail banking Corporate and Commercial Banking and Corporate Centre [member] Member ck0001649373:RetailBankingCorporateAndCommercialBankingAndCorporateCentreMember
2341 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
2342 Disclosure of probability weightings of scenarios [line items] LineItems ck0001649373:DisclosureOfProbabilityWeightingsOfScenariosLineItems
2343 ECL Concept (Monetary) For Period Credit ck0001649373:ExpectedCreditLossesAllowance
2344 1180 - Disclosure - Accounting Policies - Summary of Increase (Decrease in Profit Before Tax (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAccountingPoliciesSummaryOfIncreaseDecreaseInProfitBeforeTax
2345 Implied Table Table

*

*

 implied:Table
2346 Disclosure - Accounting Policies - Summary of Increase (Decrease in Profit Before Tax [Abstract] Abstract ck0001649373:DisclosureAccountingPoliciesSummaryOfIncreaseDecreaseInProfitBeforeTaxAbstract
2347 Increase in profit before tax due to 20 percentage increase in HPI rate Concept (Monetary) For Period Credit ck0001649373:ProfitBeforeTaxDueToTwentyPercentageIncreaseInHpiRate
2348 Increase in profit before tax due to 10 percentage increase in HPI rate Concept (Monetary) For Period Credit ck0001649373:ProfitBeforeTaxDueToTenPercentageIncreaseInHpiRate
2349 Decrease in profit before tax due to 10 percentage decrease in HPI rate Concept (Monetary) For Period Credit ck0001649373:ProfitBeforeTaxDueToTenPercentageDecreaseInHpiRate
2350 Decrease in profit before tax due to 20 percentage decrease in HPI rate Concept (Monetary) For Period Credit ck0001649373:ProfitBeforeTaxDueToTwentyPercentageDecreaseInHpiRate
2351 1181 - Disclosure - Segments - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSegmentsAdditionalInformation
2352 Disclosure of operating segments [table] Table

*

*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2353 Segments [axis] Axis ifrs-full:SegmentsAxis
2354 Segments [member] Member ifrs-full:SegmentsMember
2355 Retail banking [member] Member ck0001649373:RetailBankingMember
2356 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
2357 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
2358 Range [axis] Axis ifrs-full:RangeAxis
2359 Ranges [member] Member ifrs-full:RangesMember
2360 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2361 Top of Range [member] Member ifrs-full:TopOfRangeMember
2362 Disclosure of operating segments [line items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2363 Turnover from Small business customers Concept (Monetary) For Period Credit ck0001649373:TurnoverFromSmallBusinessCustomers
2364 Annual turnover of business Concept (Monetary) For Period Credit ck0001649373:TurnoverFromMediumAndLargeBusinessCustomers
2365 1182 - Disclosure - Segments - Summary of Results by Segment (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSegmentsSummaryOfResultsBySegment
2366 Disclosure of operating segments [table] Table

*

*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2367 Segments [axis] Axis ifrs-full:SegmentsAxis
2368 Segments [member] Member ifrs-full:SegmentsMember
2369 Retail banking [member] Member ck0001649373:RetailBankingMember
2370 Corporate and commercial banking [member] Member ck0001649373:CorporateAndCommercialBankingMember
2371 Corporate and investment banking [member] Member ck0001649373:CorporateAndInvestmentBankingMember
2372 Corporate centre [member] Member ck0001649373:CorporateCentreMember
2373 Segment consolidation items [axis] Axis ifrs-full:SegmentConsolidationItemsAxis
2374 Entity's total for segment consolidation items [member] Member ifrs-full:EntitysTotalForSegmentConsolidationItemsMember
2375 Elimination of Intersegment Amounts [member] Member ifrs-full:EliminationOfIntersegmentAmountsMember
2376 Disclosure of operating segments [line items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2377 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestRevenueExpense
2378 Non-interest income Concept (Monetary) For Period Credit ck0001649373:NonInterestIncomeExpense
2379 Total operating income Concept (Monetary) For Period Credit ck0001649373:AggregateOperatingIncomeExpense
2380 Operating expenses before credit impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001649373:OperatingExpensesBeforeCreditImpairmentLossesProvisionsAndCharges
2381 Credit impairment (losses)/releases Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
2382 Provisions for other liabilities and charges Concept (Monetary) For Period Debit ck0001649373:ProvisionsForOtherLiabilitiesAndCharges
2383 Total operating credit impairment losses, provisions and (charges)/releases Concept (Monetary) For Period Debit ck0001649373:AggregateOperatingCreditImpairmentLossesProvisionsAndCharges
2384 Profit before tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2385 Revenue from external customers Concept (Monetary) For Period Credit ifrs-full:RevenueFromContractsWithCustomers
2386 Inter-segment revenue Concept (Monetary) For Period Credit ifrs-full:RevenueAndOperatingIncome
2387 Total operating income Concept (Monetary) For Period Credit ck0001649373:AggregateOperatingIncomeExpense
2388 Revenue from external customers includes the following fee and commission income disaggregated by income type: Abstract ifrs-full:ReceivablesFromContractsWithCustomersAbstract
2389 - Current account and debit card fees Concept (Monetary) For Period Credit ck0001649373:IncomeFromCurrentAccountAndDebitCardFees
2390 - Insurance, protection and investments Concept (Monetary) For Period Credit ck0001649373:IncomeFromInsuranceProtectionAndInvestments
2391 - Credit cards Concept (Monetary) For Period Credit ck0001649373:IncomeFromCreditCards
2392 - Non-banking and other fees(3) Concept (Monetary) For Period Credit ck0001649373:IncomeFromNonBankingAndOtherFees
2393 Total fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncome
2394 Fee and commission expense Concept (Monetary) For Period Debit ifrs-full:FeeAndCommissionExpense
2395 Net fee and commission income Concept (Monetary) For Period Credit ck0001649373:FeeAndCommissionIncomeExpenseNet
2396 Customer loans Concept (Monetary) As Of Debit ck0001649373:CustomerLoansNet
2397 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
2398 Customer deposits Concept (Monetary) As Of Credit ck0001649373:CustomerDepositsNet
2399 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
2400 Average number of staff Concept (Decimal) For Period ifrs-full:AverageNumberOfEmployees
2401 1183 - Disclosure - Segments - Summary of Results by Segment (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSegmentsSummaryOfResultsBySegmentParenthetical
2402 Disclosure of operating segments [table] Table

*

*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2403 Reclassified items [axis] Axis ifrs-full:ReclassifiedItemsAxis
2404 Reclassified items [member] Member ifrs-full:ReclassifiedItemsMember
2405 Reclassification and presentational changes [member] Member ck0001649373:ReclassificationAndPresentationalChangesMember
2406 Segments [axis] Axis ifrs-full:SegmentsAxis
2407 Segments [member] Member ifrs-full:SegmentsMember
2408 Corporate centre [member] Member ck0001649373:CorporateCentreMember
2409 Disclosure of operating segments [line items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2410 Profit before tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2411 Customer loans Concept (Monetary) As Of Debit ck0001649373:CustomerLoansNet
2412 Customer deposits Concept (Monetary) As Of Credit ck0001649373:CustomerDepositsNet
2413 1184 - Disclosure - Net Interest Income - Summary of Net Interest Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNetInterestIncomeSummaryOfNetInterestIncome
2414 Implied Table Table

*

*

 implied:Table
2415 Analysis of income and expense [abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
2416 Interest and similar income: Abstract ck0001649373:InterestAndSimilarIncomeAbstract
2417 Loans and advances to customers Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnLoansAndAdvancesToCustomers
2418 Loans and advances to banks Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnLoansAndAdvancesToBanks
2419 Reverse repurchase agreements - non trading Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
2420 Other Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnOtherFinancialAssets
2421 Total interest and similar income Concept (Monetary) For Period Credit ifrs-full:RevenueFromInterest
2422 Interest expense and similar charges: Abstract ck0001649373:InterestExpenseAndSimilarChargesAbstract
2423 Deposits by customers Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnDepositsFromCustomers
2424 Deposits by banks Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnDepositsFromBanks
2425 Repurchase agreements - non trading Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnRepurchaseAgreementsAndCashCollateralOnSecuritiesLent
2426 Debt securities in issue Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnDebtInstrumentsIssued
2427 Subordinated liabilities Concept (Monetary) For Period Debit ck0001649373:InterestExpenseOnSubordinatedLiabilities
2428 Other Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnOtherFinancialLiabilities
2429 Total interest expense and similar charges Concept (Monetary) For Period Debit ifrs-full:InterestExpense
2430 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestRevenueExpense
2431 1185 - Disclosure - Net Interest Income - Summary of Net Interest Income (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNetInterestIncomeSummaryOfNetInterestIncomeParenthetical
2432 Implied Table Table

*

*

 implied:Table
2433 Analysis of income and expense [abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
2434 Interest income on financial assets at fair value through other comprehensive income Concept (Monetary) For Period Credit ifrs-full:InterestIncomeForFinancialAssetsNotAtFairValueThroughProfitOrLoss
2435 Interest expense on financial assets at fair value through other comprehensive income Concept (Monetary) For Period Debit ck0001649373:InterestExpenseNotAtFairValueThroughProfitOrLoss
2436 1186 - Disclosure - Net Interest Income - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNetInterestIncomeAdditionalInformation
2437 Implied Table Table

*

*

 implied:Table
2438 Interest And Similar Income [abstract] Abstract ck0001649373:InterestAndSimilarIncomeAbstract
2439 Interest and similar income on impaired loans Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnImpairedFinancialAssetsAccrued
2440 1187 - Disclosure - Net Fee and Commission Income - Summary of Net Fee and Commission Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNetFeeAndCommissionIncomeSummaryOfNetFeeAndCommissionIncome
2441 Disclosure of disaggregation of revenue from contracts with customers [table] Table

*

*

 ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersTable
2442 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
2443 Products and services [member] Member ifrs-full:ProductsAndServicesMember
2444 Current account and debit card fees [member] Member ck0001649373:CurrentAccountAndDebitCardFeesMember
2445 Insurance, protection and investments [member] Member ck0001649373:InsuranceProtectionAndInvestmentsMember
2446 Credit cards [member] Member ck0001649373:CreditCardsMember
2447 Non-banking and other fees [member] Member ck0001649373:NonbankingAndOtherFeesMember
2448 Net Fee And Commission Income [Line Items] LineItems ck0001649373:NetFeeAndCommissionIncomeLineItems
2449 Fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncome
2450 Fee and commission expense Concept (Monetary) For Period Debit ifrs-full:FeeAndCommissionExpense
2451 Net fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncomeExpense
2452 1188 - Disclosure - Net Trading and Other Income - Summary of Net Trading and Other Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNetTradingAndOtherIncomeSummaryOfNetTradingAndOtherIncome
2453 Implied Table Table

*

*

 implied:Table
2454 Net Trading And Other Income [abstract] Abstract ck0001649373:NetTradingAndOtherIncomeAbstract
2455 Net trading and funding of other items by the trading book Concept (Monetary) For Period Credit ifrs-full:OtherTradingIncomeExpense
2456 Net (losses)/ gains on other financial assets at fair value through profit or loss Concept (Monetary) For Period Credit ck0001649373:GainsLossesOnOtherFinancialAssetsAtFairValueThroughProfitOrLoss
2457 Net (losses)/gains on other financial liabilities at fair value through profit or loss Concept (Monetary) For Period Credit ck0001649373:GainsLossesOnOtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
2458 Net losses on derivatives managed with assets/liabilities held at fair value through profit or loss Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnChangeInFairValueOfDerivatives
2459 Hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectiveness
2460 Net profit on sale of available-for-sale assets Concept (Monetary) For Period Credit ck0001649373:GainsLossesFromDisposalOfAvailableForSaleFinancialAssets
2461 Net profit on sale of financial assets at fair value through other comprehensive income Concept (Monetary) For Period Credit ck0001649373:GainsLossesOnSaleFromDisposalOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
2462 Net income from operating lease assets Concept (Monetary) For Period Credit ifrs-full:OperatingLeaseIncome
2463 Other Concept (Monetary) For Period Credit ifrs-full:OtherIncome
2464 Net trading and other income Concept (Monetary) For Period Credit ck0001649373:NetTradingAndOtherIncome
2465 1189 - Disclosure - Net Trading and Other Income - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNetTradingAndOtherIncomeAdditionalInformation
2466 Disclosure of Subordinated Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfSubordinatedLiabilitiesTable
2467 Legal entity [axis] Axis dei:LegalEntityAxis
2468 Entity [Domain] Member dei:EntityDomain
2469 Vocalink Holdings Limited [member] Member ck0001649373:VocalinkHoldingsLimitedMember
2470 Visa Europe Ltd [member] Member ck0001649373:VisaEuropeLtdMember
2471 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
2472 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
2473 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
2474 Non-Cumulative Trust Preferred Securities [member] Member ck0001649373:NoncumulativeTrustPreferredSecuritiesMember
2475 Disclosure of subordinated liabilities [line items] LineItems ck0001649373:DisclosureOfSubordinatedLiabilitiesLineItems
2476 Fair value gains/(losses) on net trading and funding of other items by trading book Concept (Monetary) For Period Debit ck0001649373:FairValueLossesOnNetTradingAndFundingOfOtherItemsByTradingBook
2477 (Losses)/gains on equity derivatives trading desk Concept (Monetary) For Period Credit ck0001649373:GainsOnEquityDerivativesTradingDesk
2478 Net gain on equity index-linked deposits and the related economic hedges Concept (Monetary) For Period Credit ck0001649373:NetGainOnEquityIndexlinkedDepositsAndTheRelatedEconomicHedges
2479 Gain on sale of shares Concept (Monetary) For Period Credit ck0001649373:GainOnSaleOfEquitySecurities
2480 Percentage of notes purchased and redeemed Concept (Percent) As Of ck0001649373:RedemptionPercentage
2481 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
2482 Maturity year Concept (Text/String) For Period ck0001649373:CallDateOfUndatedSubordinatedLiabilities
2483 Exchange rate differences recognised Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
2484 Principally offset from cash flow hedge reserve Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax
2485 1190 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOperatingExpensesBeforeCreditImpairmentLossesProvisionsAndChargesSummaryOfOperatingExpensesBeforeCreditImpairmentLossesProvisionsAndCharges
2486 Implied Table Table

*

*

 implied:Table
2487 Expenses by nature [abstract] Abstract ifrs-full:ExpenseByNatureAbstract
2488 Staff costs: Abstract ifrs-full:ClassesOfEmployeeBenefitsExpenseAbstract
2489 Wages and salaries Concept (Monetary) For Period Debit ifrs-full:WagesAndSalaries
2490 Performance-related payments Concept (Monetary) For Period Debit ck0001649373:PerformanceRelatedPayments
2491 Social security costs Concept (Monetary) For Period Debit ifrs-full:SocialSecurityContributions
2492 Pensions costs - defined contribution plans Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
2493 Pensions costs - defined benefit plans Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedBenefitPlans
2494 Other share-based payments Concept (Monetary) For Period Debit ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
2495 Other personnel costs Concept (Monetary) For Period Debit ifrs-full:OtherEmployeeExpense
2496 Employee benefits expense Concept (Monetary) For Period Debit ifrs-full:EmployeeBenefitsExpense
2497 Other administration expenses Concept (Monetary) For Period Debit ck0001649373:OtherAdministrationExpenses
2498 Depreciation, amortisation and impairment Concept (Monetary) For Period Debit ifrs-full:DepreciationAmortisationAndImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLoss
2499 Total operating expenses before impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001649373:OperatingExpensesBeforeCreditImpairmentLossesProvisionsAndCharges
2500 1191 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Summary of Deferred Performance Awards (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOperatingExpensesBeforeCreditImpairmentLossesProvisionsAndChargesSummaryOfDeferredPerformanceAwards
2501 Disclosure of Deferred Performance Awards [table] Table

*

*

 ck0001649373:DisclosureOfDeferredPerformanceAwardsTable
2502 Maturity [axis] Axis ifrs-full:MaturityAxis
2503 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2504 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2505 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
2506 Year In Which Awards Arose [axis] Axis ck0001649373:YearInWhichAwardsAroseAxis
2507 Year In Which Awards Arose [domain] Member ck0001649373:YearInWhichAwardsAroseDomain
2508 Arising From Awards in Current Year [member] Member ifrs-full:CurrentMember
2509 Arising From Awards in Prior Year [member] Member ck0001649373:PriorPeriodMember
2510 Disclosure of deferred performance awards [line Items] LineItems ck0001649373:DisclosureOfDeferredPerformanceAwardsLineItems
2511 Cash Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsCashDeferred
2512 Shares Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsSharesDeferred
2513 Deferred performance awards Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsDeferred
2514 1192 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Summary of Amount of Bonus Awarded to Employees (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOperatingExpensesBeforeCreditImpairmentLossesProvisionsAndChargesSummaryOfAmountOfBonusAwardedToEmployees
2515 Disclosure of Amount of Bonus Awarded to Employees [table] Table

*

*

 ck0001649373:DisclosureOfAmountOfBonusAwardedToEmployeesTable
2516 Maturity [axis] Axis ifrs-full:MaturityAxis
2517 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2518 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2519 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
2520 Disclosure of amount of bonus awarded to employees [line items] LineItems ck0001649373:DisclosureOfAmountOfBonusAwardedToEmployeesLineItems
2521 Cash award - not deferred Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsCashNonDeferred
2522 - deferred Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsCashDeferred
2523 Share awards - not deferred Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsSharesNonDeferred
2524 - deferred Concept (Monetary) For Period Debit ck0001649373:PerformanceAwardsSharesDeferred
2525 Total discretionary bonus Concept (Monetary) For Period Debit ck0001649373:PerformanceAwards
2526 1193 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOperatingExpensesBeforeCreditImpairmentLossesProvisionsAndChargesAdditionalInformation
2527 Implied Table Table

*

*

 implied:Table
2528 Classes of employee benefits expense [abstract] Abstract ifrs-full:ClassesOfEmployeeBenefitsExpenseAbstract
2529 Increase in liabilities Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseInLiabilities
2530 Average number of full-time equivalent staff Concept (Decimal) For Period ifrs-full:AverageNumberOfEmployees
2531 Impairment charge Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsOtherThanGoodwill
2532 1194 - Disclosure - Audit and Other Services - Summary of Audit and Other Services (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAuditAndOtherServicesSummaryOfAuditAndOtherServices
2533 Implied Table Table

*

*

 implied:Table
2534 Disclosure of finance income costs [abstract] Abstract ck0001649373:DisclosureOfFinanceIncomeCostsAbstract
2535 Audit fees: Abstract ck0001649373:AuditFeesAbstract
2536 Fees payable to the Company's auditor and its associates for the audit of the Santander UK group's annual accounts Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForAuditServicesGroupAnnualAccounts
2537 - Audit of the Santander UK group's subsidiaries Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForAuditServicesGroupSubsidiaries
2538 Total audit fees Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForAuditServices
2539 Non-audit fees: Abstract ck0001649373:NonAuditFeesAbstract
2540 Audit-related assurance services Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForNonAuditServicesAuditRelatedServices
2541 Taxation compliance services Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForTaxServices
2542 Other assurance services Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForOtherServices
2543 Other non-audit services Concept (Monetary) For Period Debit ck0001649373:AuditorRemunerationForOtherNonauditServices
2544 Total non-audit fees Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForNonAuditServices
2545 1195 - Disclosure - Audit and Other Services - Summary of Audit and Other Services (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAuditAndOtherServicesSummaryOfAuditAndOtherServicesParenthetical
2546 Disclosure of audit fees and non audit fees [table] Table

*

*

 ck0001649373:DisclosureOfAuditFeesAndNonAuditFeesTable
2547 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
2548 Products and services [member] Member ifrs-full:ProductsAndServicesMember
2549 Prior year audit services [member] Member ck0001649373:PriorYearAuditServicesMember
2550 Disclosure of audit fees and non audit fees [Line Items] LineItems ck0001649373:DisclosureOfAuditFeesAndNonAuditFeesLineItems
2551 Auditors fee Concept (Monetary) For Period Debit ifrs-full:AuditorsRemuneration
2552 Audit-related assurance services Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForNonAuditServicesAuditRelatedServices
2553 1196 - Disclosure - Audit and Other Services - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAuditAndOtherServicesAdditionalInformation
2554 Disclosure of audit fees and non audit fees [table] Table

*

*

 ck0001649373:DisclosureOfAuditFeesAndNonAuditFeesTable
2555 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2556 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2557 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
2558 Corporate and Other Borrowers [member] Member ck0001649373:CorporateAndOtherBorrowersMember
2559 Disclosure of audit fees and non audit fees [Line Items] LineItems ck0001649373:DisclosureOfAuditFeesAndNonAuditFeesLineItems
2560 Audit fees payable for statutory audit Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForAuditServices
2561 Audit-related services related to services performed in connection with the statutory and regulatory filings Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForNonAuditServicesAuditRelatedServicesStatutoryAndRegulatoryFilings
2562 Audit-related services related to services performed in connection with securitisation, debt issuance and related work and reporting to prudential and conduct regulators Concept (Monetary) For Period Debit ck0001649373:AuditorsRemunerationForNonAuditServicesAuditRelatedServicesSecuritisationDebtIssuanceAndRelatedWorkAndReportingToPrudentialAndConductRegulators
2563 1197 - Disclosure - Credit Impairment Losses and Provisions - Summary of Impairment Losses and Provisions (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditImpairmentLossesAndProvisionsSummaryOfImpairmentLossesAndProvisions
2564 Implied Table Table

*

*

 implied:Table
2565 Disclosure of credit impairment loss and provisions [abstract] Abstract ck0001649373:DisclosureOfCreditImpairmentLossAndProvisionsAbstract
2566 Loans and advances to customers (See Note 14) Concept (Monetary) For Period Debit ck0001649373:CreditImpairmentLossesOnLoansAndAdvancesToCustomer
2567 Recoveries of loans and advances, net of collection costs (See Note 14) Concept (Monetary) For Period Debit ck0001649373:FinancialAssetsPostWriteoffRecoveries
2568 Off-balance sheet exposures (See Note 30) Concept (Monetary) For Period Debit ck0001649373:OffBalanceSheetCreditExposures
2569 Impairment loss on financial assets Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
2570 Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 30) Concept (Monetary) For Period Credit ck0001649373:ProvisionsForOtherLiabilitiesAndChargesExcludingOffBalanceSheetCreditExposures
2571 Provisions for RV and voluntary termination (See Note 14) Concept (Monetary) For Period Debit ck0001649373:ProvisionsForResidualValueAndVoluntaryTermination
2572 Provisions for other liabilities and charges Concept (Monetary) For Period Debit ck0001649373:ProvisionsForOtherLiabilitiesAndCharges
2573 Total operating impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001649373:AggregateOperatingCreditImpairmentLossesProvisionsAndCharges
2574 1198 - Disclosure - Credit Impairment Losses and Provisions - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureCreditImpairmentLossesAndProvisionsAdditionalInformation
2575 Implied Table Table

*

*

 implied:Table
2576 Disclosure of credit impairment loss and provisions [abstract] Abstract ck0001649373:DisclosureOfCreditImpairmentLossAndProvisionsAbstract
2577 Impairment losses on loans and advances to banks Concept (Monetary) For Period Debit ck0001649373:CreditImpairmentLossesOnLoansAndAdvancesToBank
2578 Impairment losses on Non-trading reverse repurchase agreements Concept (Monetary) For Period Debit ck0001649373:CreditImpairmentLossesOnNontradingReverseRepurchaseAgreements
2579 Impairment losses on other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001649373:CreditImpairmentLossesOnOtherFinancialAssetsAtAmortisedCost
2580 Impairment losses on financial assets at FVOCI Concept (Monetary) For Period Debit ck0001649373:CreditImpairmentLossesOnFinancialAssetsAtFVOCI
2581 1199 - Disclosure - Taxation - Disclosure of Tax on Profit (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTaxationDisclosureOfTaxOnProfit
2582 Implied Table Table

*

*

 implied:Table
2583 Major components of tax expense (income) [abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
2584 Current tax: Abstract ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriodsAbstract
2585 UK corporation tax on profit for the year Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncome
2586 Adjustments in respect of prior years Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForCurrentTaxOfPriorPeriod
2587 Total current tax Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriods
2588 Deferred tax: Abstract ifrs-full:DeferredTaxExpenseIncomeAbstract
2589 Charge/(credit) for the year Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncomeRelatingToOriginationAndReversalOfTemporaryDifferences
2590 Adjustments in respect of prior years Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDeferredTaxOfPriorPeriods
2591 Total deferred tax Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncome
2592 Tax on profit Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2593 1200 - Disclosure - Taxation - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTaxationAdditionalInformation
2594 Income Tax Expense Benefits [table] Table

*

*

 ck0001649373:IncomeTaxExpenseBenefitsTable
2595 Non-adjusting events after reporting period [axis] Axis ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
2596 Non-adjusting Events After Reporting Period [member] Member ifrs-full:NonadjustingEventsMember
2597 Finance (No.2) Act 2015 [member] Member ck0001649373:FinanceAct2015Member
2598 Finance (No.2) Act 2016 [member] Member ck0001649373:FinanceAct2016Member
2599 Range [axis] Axis ifrs-full:RangeAxis
2600 Ranges [member] Member ifrs-full:RangesMember
2601 Top of Range [member] Member ifrs-full:TopOfRangeMember
2602 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2603 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
2604 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
2605 Banking Entities [member] Member ck0001649373:BankingEntitiesMember
2606 Non-banking Entities [member] Member ck0001649373:NonBankingEntitiesMember
2607 Corporation Tax Rate in 2020 [member] Member ck0001649373:CorporationTaxRateIn2020Member
2608 Deferred Tax Assets That Rely on Future Profitability Excluding Timing Differences [member] Member ck0001649373:DeferredTaxAssetMember
2609 Income Tax Expense Benefits [line items] LineItems ck0001649373:IncomeTaxExpenseBenefitsLineItems
2610 Applicable tax rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
2611 Bank corporation tax surcharge Concept (Percent) For Period ck0001649373:BankCorporationTaxSurcharge
2612 Effective tax rate Concept (Percent) For Period ifrs-full:AverageEffectiveTaxRate
2613 Recognised capital losses carried forward Concept (Monetary) For Period Debit ck0001649373:RecognisedUKCapitalLossesCarriedForward
2614 Unrecognised capital losses carried forward Concept (Monetary) For Period Debit ck0001649373:UnrecognisedCapitalLossesCarriedForward
2615 Net operating losses carried forward Concept (Monetary) For Period Debit ck0001649373:NetUSOperatingLossesCarriedForward
2616 1201 - Disclosure - Taxation - Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTaxationScheduleOfTaxOnProfitBeforeTaxDiffersFromTheoreticalAmountThatAriseUsingBasicCorporationTaxRate
2617 Implied Table Table

*

*

 implied:Table
2618 Reconciliation of accounting profit multiplied by applicable tax rates [abstract] Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
2619 Profit before tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2620 Tax calculated at a tax rate of 19% (2017: 19.25%, 2016: 20.00%) Concept (Monetary) For Period Debit ifrs-full:TaxExpenseIncomeAtApplicableTaxRate
2621 Bank surcharge on profits Concept (Monetary) For Period Debit ck0001649373:TaxEffectOfBankCorporationTaxSurchargeOnProfits
2622 Non-deductible preference dividends paid Concept (Monetary) For Period Debit ck0001649373:TaxEffectOfNonDeductiblePreferenceDividendsPaid
2623 Non-deductible UK Bank Levy Concept (Monetary) For Period Debit ck0001649373:TaxEffectOfNonDeductibleBankLevy
2624 Non-deductible conduct remediation, fines and penalties Concept (Monetary) For Period Debit ck0001649373:TaxEffectOfNonDeductibleConductRemediationFinesAndPenalties
2625 Other non-deductible costs and non-taxable income Concept (Monetary) For Period Debit ifrs-full:OtherTaxEffectsForReconciliationBetweenAccountingProfitAndTaxExpenseIncome
2626 Effect of change in tax rate on deferred tax provision Concept (Monetary) For Period Debit ifrs-full:TaxEffectFromChangeInTaxRate
2627 Adjustment to prior year provisions Concept (Monetary) For Period Debit ck0001649373:TaxEffectOfPriorYearAdjustments
2628 Tax charge Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2629 1202 - Disclosure - Taxation - Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTaxationScheduleOfTaxOnProfitBeforeTaxDiffersFromTheoreticalAmountThatAriseUsingBasicCorporationTaxRateParenthetical
2630 Implied Table Table

*

*

 implied:Table
2631 Reconciliation of accounting profit multiplied by applicable tax rates [abstract] Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
2632 Standard tax rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
2633 1203 - Disclosure - Taxation - Disclosure of Movements in Current Tax Assets and Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTaxationDisclosureOfMovementsInCurrentTaxAssetsAndLiabilities
2634 Implied Table Table

*

*

 implied:Table
2635 Current Tax Assets and Liabilities [abstract] Abstract ck0001649373:CurrentTaxAssetsAndLiabilitiesAbstract
2636 Assets Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssets
2637 Liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilities
2638 Beginning Balance Concept (Monetary) As Of Credit ck0001649373:CurrentTaxLiabilityAsset
2639 Income statement charge Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriods
2640 Other comprehensive income credit/(charge) Concept (Monetary) For Period Debit ck0001649373:CurrentTaxExpenseIncomeRecognisedInOtherComprehensiveIncome
2641 Corporate income tax paid Concept (Monetary) For Period Credit ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities
2642 Other movements Concept (Monetary) For Period Debit ck0001649373:IncreaseDecreaseInOtherCurrentTaxLiabilityAsset
2643 Ending Balance Concept (Monetary) As Of Credit ck0001649373:CurrentTaxLiabilityAsset
2644 Assets Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssets
2645 Liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilities
2646 1204 - Disclosure - Taxation - Disclosure of Deferred Tax Assets and Liabilities Including Movement in Deferred Tax Account (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTaxationDisclosureOfDeferredTaxAssetsAndLiabilitiesIncludingMovementInDeferredTaxAccount
2647 Disclosure of temporary difference, unused tax losses and unused tax credits [table] Table

*

*

 ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
2648 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
2649 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
2650 Fair Value of Financial Instruments [member] Member ck0001649373:FairValueOfFinancialInstrumentsMember
2651 Pension Remeasurement [member] Member ck0001649373:PensionRemeasurementMember
2652 Cash Flow Hedges [member] Member ifrs-full:CashFlowHedgesMember
2653 Available-for-Sale [member] Member ck0001649373:AvailableForSaleMember
2654 Fair Value Reserves Related to Gains or Losses on Cash Flow Hedges [Member] Member ck0001649373:FairValueReserveMember
2655 Tax Losses Carried Forward [member] Member ifrs-full:UnusedTaxLossesMember
2656 Accelerated Tax Depreciation [member] Member ck0001649373:AcceleratedTaxDepreciationMember
2657 Other temporary differences [member] Member ifrs-full:OtherTemporaryDifferencesMember
2658 Disclosure of temporary difference, unused tax losses and unused tax credits [line items] LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
2659 Beginning Balance Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
2660 Adoption of IFRS 9 (see Note 1) Concept (Monetary) For Period Debit ck0001649373:DeferredTaxLiabilityAssetAdjustmentForAdoptionOfIfrs9
2661 Beginning Balance, After adoption of IFRS 9 Concept (Monetary) As Of Credit ck0001649373:DeferredTaxLiabilityAssetAfterAdoptionOfIfrs9
2662 Income statement (charge)/credit Concept (Monetary) For Period ifrs-full:DeferredTaxExpenseIncomeRecognisedInProfitOrLoss
2663 Transfers/reclassifications Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseThroughTransfersReclassifcationsDeferredTaxLiabilityAsset
2664 Credited/(charged) to other comprehensive income Concept (Monetary) For Period ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncome
2665 Ending Balance Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
2666 1205 - Disclosure - Dividends on Ordinary Shares - Disclosure of Dividends on Ordinary Shares Declared and Paid (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDividendsOnOrdinarySharesDisclosureOfDividendsOnOrdinarySharesDeclaredAndPaid
2667 Disclosure of Dividends on Ordinary Shares [table] Table

*

*

 ck0001649373:DisclosureOfDividendsOnOrdinarySharesTable
2668 Dividend Payments Made [axis] Axis ck0001649373:DividendPaymentsMadeAxis
2669 Dividend Payments Made [domain] Member ck0001649373:DividendPaymentsMadeDomain
2670 First Interim [member] Member ck0001649373:FirstInterimMember
2671 Second Interim [member] Member ck0001649373:SecondInterimMember
2672 Third Interim [member] Member ck0001649373:ThirdInterimMember
2673 Disclosure of Dividends on Ordinary Shares [Line Items] LineItems ck0001649373:DisclosureOfDividendsOnOrdinarySharesLineItems
2674 Dividend per share Concept (Share) For Period ifrs-full:DividendsPaidOrdinarySharesPerShare
2675 Dividends Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToOwnersOfParent
2676 1206 - Disclosure - Dividends on Ordinary Shares - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDividendsOnOrdinarySharesAdditionalInformation
2677 Implied Table Table

*

*

 implied:Table
2678 Dividends On Ordinary Shares [abstract] Abstract ck0001649373:DividendsOnOrdinarySharesAbstract
2679 Dividends declared Concept (Monetary) For Period Debit ck0001649373:DividendsDeclaredOrdinaryShares
2680 Dividends paid Concept (Monetary) For Period Debit ifrs-full:DividendsPaidOrdinaryShares
2681 Percentage of dividend on recurring earnings Concept (Percent) For Period ck0001649373:DividendOnRecurringEarningsPercentage
2682 1207 - Disclosure - Trading Assets - Disclosure of Trading Assets (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTradingAssetsDisclosureOfTradingAssets
2683 Disclosure Of Financial Assets Held For Trading [table] Table

*

*

 ck0001649373:DisclosureOfFinancialAssetsHeldForTradingTable
2684 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2685 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2686 Securities Purchased Under Resale Agreements [member] Member ck0001649373:SecuritiesPurchasedUnderResaleAgreementsMember
2687 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
2688 Equity securities [member] Member ifrs-full:TradingEquitySecuritiesMember
2689 Cash Collateral Associated with Trading Balances [member] Member ck0001649373:CashCollateralAssociatedWithTradingBalancesMember
2690 Short-term loans [member] Member ck0001649373:ShortTermLoansMember
2691 Disclosure of financial assets held for trading [line items] LineItems ck0001649373:DisclosureOfFinancialAssetsHeldForTradingLineItems
2692 Total trading assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2693 1208 - Disclosure - Derivative Financial Instruments - Notional Amounts and Fair Values of Derivatives (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsNotionalAmountsAndFairValuesOfDerivatives
2694 Disclosure of detailed information about hedges [table] Table

*

*

 ifrs-full:DisclosureOfHedgeAccountingTable
2695 Measurement [axis] Axis ifrs-full:MeasurementAxis
2696 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
2697 Fair Value [member] Member ifrs-full:AtFairValueMember
2698 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2699 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2700 Exchange Rate Contracts [member] Member ifrs-full:CurrencySwapContractMember
2701 Interest Rate Contracts [member] Member ifrs-full:InterestRateSwapContractMember
2702 Equity and Credit Contracts [member] Member ck0001649373:EquityAndCreditContractsMember
2703 Equity Investments [Member] Member ifrs-full:EquityInvestmentsMember
2704 Netting adjustments [member] Member ck0001649373:NettingAdjustmentsMember
2705 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
2706 Hedges [member] Member ifrs-full:TypesOfHedgesMember
2707 Fair Value Hedges [member] Member ifrs-full:FairValueHedgesMember
2708 Cash Flow Hedges [member] Member ifrs-full:CashFlowHedgesMember
2709 Hedging instruments [axis] Axis ifrs-full:HedgingInstrumentsAxis
2710 Hedging instruments [member] Member ifrs-full:HedgingInstrumentsMember
2711 Derivatives Held for Trading [member] Member ck0001649373:DerivativesHeldForTradingMember
2712 Derivatives Held for Hedging [member] Member ck0001649373:DerivativesHeldForHedgingMember
2713 Disclosure of detailed information about hedges [line items] LineItems ifrs-full:DisclosureOfHedgeAccountingLineItems
2714 Derivative notional Concept (Monetary) As Of ifrs-full:NotionalAmount
2715 Fair value assets Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
2716 Fair value liabilities Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
2717 1209 - Disclosure - Derivative Financial Instruments - Notional Amounts and Fair Values of Derivatives (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsNotionalAmountsAndFairValuesOfDerivativesParenthetical
2718 Disclosure of detailed information about hedges [table] Table

*

*

 ifrs-full:DisclosureOfHedgeAccountingTable
2719 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2720 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2721 Derivative Assets [member] Member ck0001649373:DerivativeAssetsMember
2722 Derivative Liabilities [Member] Member ck0001649373:DerivativeLiabilitiesMember
2723 Disclosure of detailed information about hedges [line items] LineItems ifrs-full:DisclosureOfHedgeAccountingLineItems
2724 Cash collateral received that had been offset against the gross derivative assets Concept (Monetary) As Of Credit ifrs-full:CashCollateralReceivedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
2725 Cash collateral paid that had been offset against the gross derivative liabilities Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
2726 1210 - Disclosure - Derivative Financial Instruments - Analysis of the Notional and Fair Values of Derivatives by Trading and Settlement Method (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsAnalysisOfTheNotionalAndFairValuesOfDerivativesByTradingAndSettlementMethod
2727 Disclosure of Analysis of Notional and Fair Values of Derivatives by Trading and Settlement Method [table] Table

*

*

 ck0001649373:DisclosureOfAnalysisOfNotionalAndFairValuesOfDerivativesByTradingAndSettlementMethodTable
2728 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2729 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2730 Traded on Recognised Exchanges [member] Member ck0001649373:TradedOnRecognisedExchangesMember
2731 Settled by Central Counterparties [member] Member ck0001649373:SettledByCentralCounterpartiesMember
2732 Not Settled by Central Counterparties [member] Member ck0001649373:NotSettledByCentralCounterpartiesMember
2733 Traded Over the Counter [member] Member ck0001649373:TradedOverTheCounterMember
2734 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2735 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2736 Exchange Rate Contracts [member] Member ifrs-full:CurrencySwapContractMember
2737 Interest Rate Contracts [member] Member ifrs-full:InterestRateSwapContractMember
2738 Equity and Credit Contracts [member] Member ck0001649373:EquityAndCreditContractsMember
2739 Analysis of notional and fair values of derivatives by trading and settlement method [line item] LineItems ck0001649373:DisclosureOfAnalysisOfNotionalAndFairValuesOfDerivativesByTradingAndSettlementMethodLineItems
2740 Derivative notional Concept (Monetary) As Of ifrs-full:NotionalAmount
2741 Assets traded over the counter Concept (Monetary) As Of Debit ck0001649373:TradingDerivativeAssets
2742 Liabilities traded over the counter Concept (Monetary) As Of Credit ck0001649373:TradingDerivativeLiabilities
2743 1211 - Disclosure - Derivative Financial Instruments - Summary of Fixed Rate Instruments Hedged (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfFixedRateInstrumentsHedged
2744 Disclosure of detailed information about hedged items [table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutHedgedItemsTable
2745 Hedging instruments [axis] Axis ifrs-full:HedgingInstrumentsAxis
2746 Hedging instruments [member] Member ifrs-full:HedgingInstrumentsMember
2747 Fixed rate mortgages [member] Member ck0001649373:FixedRateMortgagesMember
2748 Fixed rate loans [member] Member ck0001649373:FixedRateLoansMember
2749 Reverse repurchase agreements [member] Member ck0001649373:ReverseRepurchaseAgreementsMember
2750 Investment assets [member] Member ck0001649373:InvestmentAssetsMember
2751 Fixed rate savings [member] Member ck0001649373:FixedRateSavingsMember
2752 Disclosure of detailed information about hedged items [line items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutHedgedItemsLineItems
2753 Designated benchmark instrument rate Concept (Text/String) For Period ck0001649373:DesignatedBenchmarkInstrumentRate
2754 Currency Concept (Text/String) For Period ck0001649373:UnderlyingCurrency
2755 1212 - Disclosure - Derivative Financial Instruments - Summary of Maturity Profile and Average Price/Rate of Hedging Instruments Used in Hedging Strategies (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfMaturityProfileAndAveragePriceRateOfHedgingInstrumentsUsedInHedgingStrategies
2756 Disclosure of nature and extent of risks arising from financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfNatureAndExtentOfRisksArisingFromFinancialInstrumentsTable
2757 Maturity [axis] Axis ifrs-full:MaturityAxis
2758 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2759 Less Than One Month [member] Member ck0001649373:LessThanOneMonthMember
2760 Greater Than 1 and Less Than 3 Months [member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanThreeMonthsMember
2761 Later Than Three Months and Not Later Than One Year [member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanOneYearMember
2762 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2763 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
2764 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2765 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2766 Interest Rate Contracts [member] Member ifrs-full:InterestRateSwapContractMember
2767 Exchange Rate Contracts [member] Member ifrs-full:CurrencySwapContractMember
2768 Equity derivative contracts [member] Member ck0001649373:EquityDerivativeContractsMember
2769 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2770 Risks [member] Member ifrs-full:TypesOfRisksMember
2771 Interest Rate Risks [member] Member ifrs-full:InterestRateRiskMember
2772 Interest Rate And Foreign Currency Risk [member] Member ck0001649373:InterestRateAndForeignCurrencyRiskMember
2773 Currency Risk [member] Member ifrs-full:CurrencyRiskMember
2774 Equity Risks [member] Member ifrs-full:EquityPriceRiskMember
2775 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
2776 Hedges [member] Member ifrs-full:TypesOfHedgesMember
2777 Fair Value Hedges [member] Member ifrs-full:FairValueHedgesMember
2778 Cash Flow Hedges [member] Member ifrs-full:CashFlowHedgesMember
2779 Currency [Axis] Axis srt:CurrencyAxis
2780 All Currencies [Domain] Member currency:AllCurrenciesDomain
2781 United Kingdom, Pounds [member] Member currency:GBP
2782 Euro Member Countries, Euro [member] Member currency:EUR
2783 United States of America, Dollars [member] Member currency:USD
2784 Disclosure of nature and extent of risks arising from financial instruments [line items] LineItems ifrs-full:DisclosureOfNatureAndExtentOfRisksArisingFromFinancialInstrumentsLineItems
2785 Nominal amount Concept (Monetary) As Of ifrs-full:NotionalAmount
2786 Average GBP - JPY exchange rate Concept (Decimal) As Of ck0001649373:AverageGBPJPYExchangeRate
2787 Average fixed interest rate Concept (Decimal) As Of ck0001649373:AverageFixedInterestRate
2788 Average GBP - EUR exchange rate Concept (Decimal) As Of ck0001649373:AverageGBPEURExchangeRate
2789 Average GBP - USD exchange rate Concept (Decimal) As Of ck0001649373:AverageGBPUSDExchangeRate
2790 1213 - Disclosure - Derivative Financial Instruments - Summary of Net Gains Or Losses Arising from Fair Value and Cash Flow Hedges Included in Net Trading and Other Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfNetGainsOrLossesArisingFromFairValueAndCashFlowHedgesIncludedInNetTradingAndOtherIncome
2791 Disclosure of detailed information about hedges [table] Table

*

*

 ifrs-full:DisclosureOfHedgeAccountingTable
2792 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
2793 Hedges [member] Member ifrs-full:TypesOfHedgesMember
2794 Fair Value and Cash Flow Hedges [member] Member ck0001649373:FairValueAndCashFlowHedgesMember
2795 Disclosure of detailed information about hedges [line items] LineItems ifrs-full:DisclosureOfHedgeAccountingLineItems
2796 Gains/(losses) on hedging instruments Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnHedgingInstrument
2797 (Losses)/gains on hedged items attributable to hedged risks Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnHedgedItemAttributableToHedgedRisk
2798 Fair value hedging ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnChangeInFairValueOfHedgingInstrumentUsedAsBasisForRecognisingHedgeIneffectiveness
2799 Cash flow hedging ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnIneffectivenessOfCashFlowHedgesRecognisedInProfitOrLoss
2800 Hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectiveness
2801 1214 - Disclosure - Derivative Financial Instruments - Summary of Information About Hedging Ineffectiveness by Risk Category (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfInformationAboutHedgingIneffectivenessByRiskCategory
2802 Disclosure of detailed information about hedges [table] Table

*

*

 ifrs-full:DisclosureOfHedgeAccountingTable
2803 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
2804 Hedges [member] Member ifrs-full:TypesOfHedgesMember
2805 Fair Value Hedges [member] Member ifrs-full:FairValueHedgesMember
2806 Cash Flow Hedges [member] Member ifrs-full:CashFlowHedgesMember
2807 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2808 Risks [member] Member ifrs-full:TypesOfRisksMember
2809 Interest Rate Risks [member] Member ifrs-full:InterestRateRiskMember
2810 Interest Rate And Foreign Currency Risk [member] Member ck0001649373:InterestRateAndForeignCurrencyRiskMember
2811 Currency Risk [member] Member ifrs-full:CurrencyRiskMember
2812 Equity Risks [member] Member ifrs-full:EquityPriceRiskMember
2813 Disclosure of detailed information about hedges [line items] LineItems ifrs-full:DisclosureOfHedgeAccountingLineItems
2814 Income statement line item affected by the reclassification Concept (Text/String) For Period ifrs-full:DescriptionOfLineItemInStatementOfComprehensiveIncomeThatIncludesReclassificationAdjustments
2815 Changes in FV of hedging instruments to calculate hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnChangeInFairValueOfHedgingInstrumentUsedAsBasisForRecognisingHedgeIneffectiveness
2816 Changes in value of hedging instrument recognised in OCI Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectivenessRecognisedInOtherComprehensiveIncome
2817 Changes in FV of hedged items to calculate hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnChangeInFairValueOfHedgedItemUsedAsBasisForRecognisingHedgeIneffectiveness
2818 Hedge ineffectiveness recognised in income statement Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectivenessRecognisedInProfitOrLoss
2819 Amount reclassified from cash flow hedging reserve to income statement Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesForWhichHedgedItemAffectedProfitOrLossNetOfTax
2820 1215 - Disclosure - Derivative Financial Instruments - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsAdditionalInformation
2821 Implied Table Table

*

*

 implied:Table
2822 Disclosure Of Derivative Financial Instruments [abstract] Abstract ck0001649373:DisclosureOfDerivativeFinancialInstrumentsAbstract
2823 Ceased cash flow hedge accounting Concept (Monetary) As Of Credit ifrs-full:AccumulatedFairValueHedgeAdjustmentRemainingInStatementOfFinancialPositionForHedgedItemThatCeasedToBeAdjustedForHedgingGainsAndLossesLiabilities
2824 1216 - Disclosure - Derivative Financial Instruments - Summary of Reconciliation by Risk Category of Components of Equity and Analysis of Other Comprehensive Income Items Resulting from Hedge Accounting (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfReconciliationByRiskCategoryOfComponentsOfEquityAndAnalysisOfOtherComprehensiveIncomeItemsResultingFromHedgeAccounting
2825 Disclosure of detailed information about hedges [table] Table

*

*

 ifrs-full:DisclosureOfHedgeAccountingTable
2826 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2827 Risks [member] Member ifrs-full:TypesOfRisksMember
2828 Interest Rate Risks [member] Member ifrs-full:InterestRateRiskMember
2829 Foreign Currency Risk [member] Member ck0001649373:ForeignCurrencyRiskMember
2830 Equity Risks [member] Member ifrs-full:EquityPriceRiskMember
2831 Interest Rate And Foreign Currency Risk [member] Member ck0001649373:InterestRateAndForeignCurrencyRiskMember
2832 Disclosure of detailed information about hedges [line items] LineItems ifrs-full:DisclosureOfHedgeAccountingLineItems
2833 Beginning Balance Concept (Monetary) As Of Credit ifrs-full:ReserveOfCashFlowHedges
2834 Effective portion of changes in fair value Concept (Monetary) For Period Credit ck0001649373:GainsLossesOnCashFlowHedgesEffectivePortionOfChangesInFairValue
2835 Income statement transfers Concept (Monetary) For Period Credit ck0001649373:GainsLossesOnCashFlowHedgesIncomeStatementTransfers
2836 Ending Balance Concept (Monetary) As Of Credit ifrs-full:ReserveOfCashFlowHedges
2837 1217 - Disclosure - Derivative Financial Instruments - Summary of Details of Hedged Exposures by Hedging Strategies (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfDetailsOfHedgedExposuresByHedgingStrategies
2838 Disclosure of detailed information about hedges [table] Table

*

*

 ifrs-full:DisclosureOfHedgeAccountingTable
2839 Legal entity [axis] Axis dei:LegalEntityAxis
2840 Entity [Domain] Member dei:EntityDomain
2841 Santander UK Group [member] Member ck0001649373:SantanderUKGroupMember
2842 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
2843 Assets [member] Member ifrs-full:ClassesOfAssetsMember
2844 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
2845 Other financial assets at amortised cost [member] Member ck0001649373:OtherFinancialAssetsMeasuredAtAmortizedCostMember
2846 Reverse repo agreement non trading [member] Member ck0001649373:ReverseRepoAgreementMember
2847 Other financial assets at fair value through other comprehensive income [member] Member ck0001649373:OtherFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeMember
2848 Deposits by customers [member] Member ck0001649373:DepositsByCustomersMember
2849 Deposits by banks [member] Member ck0001649373:DepositsByBanksMember
2850 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
2851 Subordinated liabilities [member] Member ck0001649373:SubordinatedLiabilitiesMember
2852 Loans and advances to banks [member] Member ck0001649373:LoansAndAdvancesToBanksMember
2853 Other financial assets measured at fair value through other comprehensive income [member] Member ck0001649373:OtherFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember
2854 Highly probable forecast transactions [member] Member ck0001649373:HighlyProbableForecastTransactionsMember
2855 Other Liabilities [member] Member ck0001649373:OtherLiabilitiesMember
2856 Debt securities in issue and loans and advances to customers [member] Member ck0001649373:DebtSecuritiesInIssueAndLoansAndAdvancesToCustomersMember
2857 Subordinated Liabilities and loans and advances to customers [member] Member ck0001649373:SubordinatedLiabilitiesAndLoansAndAdvancesToCustomersMember
2858 Types of hedges [axis] Axis ifrs-full:TypesOfHedgesAxis
2859 Hedges [member] Member ifrs-full:TypesOfHedgesMember
2860 Fair Value Hedges [member] Member ifrs-full:FairValueHedgesMember
2861 Cash Flow Hedges [member] Member ifrs-full:CashFlowHedgesMember
2862 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2863 Risks [member] Member ifrs-full:TypesOfRisksMember
2864 Interest Rate Risks [member] Member ifrs-full:InterestRateRiskMember
2865 Interest Rate And Foreign Currency Risk [member] Member ck0001649373:InterestRateAndForeignCurrencyRiskMember
2866 Currency Risk [member] Member ifrs-full:CurrencyRiskMember
2867 Equity Risks [member] Member ifrs-full:EquityPriceRiskMember
2868 Disclosure of detailed information about hedges [line items] LineItems ifrs-full:DisclosureOfHedgeAccountingLineItems
2869 Carrying value of assets Concept (Monetary) As Of Debit ifrs-full:HedgedItemAssets
2870 Carrying value of liabilities Concept (Monetary) As Of Credit ifrs-full:HedgedItemLiabilities
2871 Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item assets Concept (Monetary) As Of Debit ifrs-full:AccumulatedFairValueHedgeAdjustmentOnHedgedItemIncludedInCarryingAmountAssets
2872 Accumulated amount of FV hedge adjustments on hedged item in carrying value of hedged item liabilities Concept (Monetary) As Of Credit ifrs-full:AccumulatedFairValueHedgeAdjustmentOnHedgedItemIncludedInCarryingAmountLiabilities
2873 Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks assets Concept (Monetary) As Of Debit ck0001649373:AccumulatedFairValueOfHedgedAdjustmentsForPortfolioHedgeOfInterestRateRisksAssets
2874 Accumulated amount of FV hedge adjustments for portfolio hedge of interest rate risks liabilities Concept (Monetary) As Of Credit ck0001649373:AccumulatedFairValueOfHedgedAdjustmentsForPortfolioHedgeOfInterestRateRisksLiabilities
2875 Change in value used for calculating hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnChangeInFairValueOfHedgedItemUsedAsBasisForRecognisingHedgeIneffectiveness
2876 Accumulated amount of FV hedge adjustments on balance sheet for discontinued hedges Concept (Monetary) As Of Credit ck0001649373:AccumulatedFairValueHedgeAdjustmentsOnBalanceSheetForDiscontinuedHedges
2877 Cash flow hedge reserve Concept (Monetary) As Of Credit ifrs-full:ReserveOfCashFlowHedges
2878 Balances on cash flow hedge reserve where hedge accounting is no longer applied Concept (Monetary) As Of Credit ifrs-full:ReserveOfCashFlowHedgesHedgingRelationshipsForWhichHedgeAccountingIsNoLongerApplied
2879 1218 - Disclosure - Other Financial Assets at Fair Value Through Profit or Loss - Summary of Other Financial Assets at Fair Value Through Profit or Loss (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialAssetsAtFairValueThroughProfitOrLossSummaryOfOtherFinancialAssetsAtFairValueThroughProfitOrLoss
2880 Disclosure of financial assets designated as measured at fair value through profit or loss [table] Table

*

*

 ck0001649373:DisclosureOfFinancialAssetsDesignatedAsMeasuredAtFairValueThroughProfitOrLossTable
2881 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
2882 Assets [member] Member ifrs-full:ClassesOfAssetsMember
2883 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
2884 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
2885 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
2886 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
2887 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2888 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2889 Loans to Housing Associations [member] Member ck0001649373:LoansToHousingAssociationsMember
2890 Other Loans [member] Member ck0001649373:OtherLoansMember
2891 Disclosure of other financial assets at fair value through profit or loss [Line Items] LineItems ck0001649373:DisclosureOfOtherFinancialAssetsAtFairValueThroughProfitOrLossLineItems
2892 Loans Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
2893 1219 - Disclosure - Other Financial Assets at Fair Value Through Profit or Loss - Summary of Other Financial Assets at Fair Value Through Profit or Loss (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialAssetsAtFairValueThroughProfitOrLossSummaryOfOtherFinancialAssetsAtFairValueThroughProfitOrLossParenthetical
2894 Implied Table Table

*

*

 implied:Table
2895 Financial assets at fair value through profit or loss [abstract] Abstract ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossAbstract
2896 Financial assets designated at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
2897 Financial assets mandatorily at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
2898 1220 - Disclosure - Other Financial Assets at Fair Value Through Profit or Loss - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialAssetsAtFairValueThroughProfitOrLossAdditionalInformation
2899 Disclosure of financial assets designated as measured at fair value through profit or loss [table] Table

*

*

 ck0001649373:DisclosureOfFinancialAssetsDesignatedAsMeasuredAtFairValueThroughProfitOrLossTable
2900 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
2901 Assets [member] Member ifrs-full:ClassesOfAssetsMember
2902 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
2903 Disclosure of other financial assets at fair value through profit or loss [Line Items] LineItems ck0001649373:DisclosureOfOtherFinancialAssetsAtFairValueThroughProfitOrLossLineItems
2904 Financial assets mandatorily at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
2905 Net (loss)/gain attributable to changes in credit risk for loans and advances at fair value through profit or loss Concept (Monetary) For Period Debit ifrs-full:ChangesInFairValueOfLoansOrReceivablesAttributableToChangesInCreditRiskOfFinancialAssets
2906 Cumulative net loss attributable to changes in credit risk for loans and advances at fair value through profit or loss Concept (Monetary) As Of Debit ifrs-full:AccumulatedChangesInFairValueOfLoanOrReceivableAttributableToChangesInCreditRiskOfFinancialAssets
2907 1221 - Disclosure - Loans and Advances to Customers - Summary of Net Loans and Advances to Customers (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToCustomersSummaryOfNetLoansAndAdvancesToCustomers
2908 Implied Table Table

*

*

 implied:Table
2909 Net Loans and Advances to Customers [abstract] Abstract ck0001649373:NetLoansAndAdvancesToCustomersAbstract
2910 Loans secured on residential properties Concept (Monetary) As Of Debit ck0001649373:LoansSecuredOnResidentialProperties
2911 Corporate loans Concept (Monetary) As Of Debit ifrs-full:CorporateLoans
2912 Finance leases Concept (Monetary) As Of Debit ifrs-full:FinanceLeaseReceivables
2913 Other unsecured loans Concept (Monetary) As Of Debit ck0001649373:OtherUnsecuredLoans
2914 Amounts due from fellow Banco Santander subsidiaries and joint ventures Concept (Monetary) As Of Debit ifrs-full:TradeAndOtherReceivablesDueFromRelatedParties
2915 Loans and advances to customers Concept (Monetary) As Of Debit ck0001649373:LoansAndAdvancesToCustomersGross
2916 Credit impairment loss allowances on loans and advances to customers Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
2917 RV and voluntary termination provisions on finance leases Concept (Monetary) As Of Credit ck0001649373:ResidualValueAndVoluntaryTerminationProvisions
2918 Net loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
2919 1222 - Disclosure - Loans and Advances to Customers - Summary of Movement in Impairment Loss Allowances (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToCustomersSummaryOfMovementInImpairmentLossAllowances
2920 Movement in impairment loss allowances for loan and advances to customers [table] Table

*

*

 ck0001649373:MovementInImpairmentLossAllowancesForLoanAndAdvancesToCustomersTable
2921 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2922 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2923 Advances secured on residential property [member] Member ck0001649373:AdvancesSecuredOnResidentialPropertyMember
2924 Corporate loans [member] Member ifrs-full:CorporateLoansMember
2925 Finance leases [member] Member ifrs-full:LeaseReceivablesMember
2926 Other unsecured advances [member] Member ck0001649373:OtherUnsecuredLoansMember
2927 Movement in impairment loss allowances for loan and advances to customers [line items] LineItems ck0001649373:MovementInImpairmentLossAllowancesForLoanAndAdvancesToCustomersLineItems
2928 Beginning balance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
2929 Adoption of IFRS 9 (see Note 1) Concept (Monetary) For Period Debit ck0001649373:AdjustmentForAdoptionOfIFRS9AllowanceAccountForCreditLossesOfFinancialAssets
2930 Re-allocation of ECL on off-balance sheet exposures Concept (Monetary) For Period Debit ck0001649373:ReallocationOfExpectedCreditLossOnUndrawnExposures
2931 Balance at 1 January 2018 Concept (Monetary) As Of Credit ck0001649373:AllowanceAccountForCreditLossesOfFinancialAssetOnAdoptionOfIFRS9
2932 (Release)/charge to the income statement (see Note 8) Concept (Monetary) For Period Debit ck0001649373:ImpairmentLossesOnLoansAndAdvancesToCustomer
2933 Write-offs and other items Concept (Monetary) For Period Debit ifrs-full:UtilisationAllowanceAccountForCreditLossesOfFinancialAssets
2934 Ending balance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
2935 Observed Concept (Monetary) As Of Credit ck0001649373:ImpairmentAllowancesAgainstLoansAndAdvancesCustomersObserved
2936 Incurred but not yet observed Concept (Monetary) As Of Debit ck0001649373:ImpairmentAllowancesIncurredButNotYetObserved
2937 Recoveries, net of collection costs (see Note 8) Concept (Monetary) For Period ifrs-full:ReversalAllowanceAccountForCreditLossesOfFinancialAssets
2938 1223 - Disclosure - Loans and Advances to Customers - Summary of Movement in Impairment Loss Allowances (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToCustomersSummaryOfMovementInImpairmentLossAllowancesParenthetical
2939 Implied Table Table

*

*

 implied:Table
2940 Disclosure of impairment loss recognised or reversed for cash-generating unit [abstract] Abstract ifrs-full:DisclosureOfImpairmentLossRecognisedOrReversedAbstract
2941 Mortgage write-offs of financial assets Concept (Monetary) For Period Debit ck0001649373:MortgageWriteoffsIncludingEffectOfDiscounting
2942 Contractual amount outstanding on financial assets, written off Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsWrittenOffDuringReportingPeriodAndStillSubjectToEnforcementActivityContractualAmountOutstanding
2943 1224 - Disclosure - Loans and Advances to Customers - Summary of Finance Lease and Hire Purchase Contract Receivables (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToCustomersSummaryOfFinanceLeaseAndHirePurchaseContractReceivables
2944 Disclosure of finance costs and unwinding of obligations [table] Table

*

*

 ck0001649373:DisclosureOfFinanceCostsAndUnwindingOfObligationsTable
2945 Maturity [axis] Axis ifrs-full:MaturityAxis
2946 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2947 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2948 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2949 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
2950 Disclosure of finance lease and hire purchase contract receivables [line items] LineItems ck0001649373:DisclosureOfFinanceLeaseAndHirePurchaseContractReceivablesLineItems
2951 Gross investment Concept (Monetary) As Of Debit ifrs-full:GrossInvestmentInFinanceLease
2952 Unearned finance income Concept (Monetary) As Of Debit ifrs-full:UnearnedFinanceIncomeOnFinanceLease
2953 Net investment Concept (Monetary) As Of Debit ifrs-full:NetInvestmentInFinanceLease
2954 1225 - Disclosure - Loans and Advances To Customers - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToCustomersAdditionalInformation
2955 Implied Table Table

*

*

 implied:Table
2956 Disclosure of finance lease and hire purchase contract receivables [abstract] Abstract ck0001649373:DisclosureOfFinanceLeaseAndHirePurchaseContractReceivablesAbstract
2957 Unguaranteed residual value of leases Concept (Monetary) As Of Debit ifrs-full:DiscountedUnguaranteedResidualValueOfAssetsSubjectToFinanceLease
2958 Contingent rent income Concept (Monetary) As Of Credit ck0001649373:ContingentRentIncome
2959 1226 - Disclosure - Securitisations and Covered Bonds - Analysis of Securitisations and Covered Bonds (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSecuritisationsAndCoveredBondsAnalysisOfSecuritisationsAndCoveredBonds
2960 Disclosure of securitisations and covered bonds [table] Table

*

*

 ck0001649373:DisclosureOfSecuritisationsAndCoveredBondsTable
2961 Securitisation By Company Name [axis] Axis ck0001649373:SecuritisationByCompanyNameAxis
2962 Securitisation By Company Name [domain] Member ck0001649373:SecuritisationByCompanyNameDomain
2963 Holmes [member] Member ck0001649373:HolmesMember
2964 Fosse [member] Member ck0001649373:FosseMember
2965 Langton [member] Member ck0001649373:LangtonMember
2966 Auto ABS UK Loans [member] Member ck0001649373:AutoABSUKLoansMember
2967 Euro 35bn Global Covered Bond Programme [member] Member ck0001649373:EuroThirtyFiveBillionGlobalCoveredBondProgrammeMember
2968 Motor [member] Member ck0001649373:MotorMember
2969 Securitization By Program Name [axis] Axis ck0001649373:SecuritizationByProgramNameAxis
2970 Securitization By Program Name [domain] Member ck0001649373:SecuritizationByProgramNameDomain
2971 Covered Bond Programme [member] Member ck0001649373:CoveredBondProgrammeMember
2972 Securitisation Programmes [member] Member ck0001649373:SecuritisationProgrammesMember
2973 Type Of Securitisation [axis] Axis ck0001649373:TypeOfSecuritisationAxis
2974 Type Of Securitisation [domain] Member ck0001649373:TypeOfSecuritisationDomain
2975 Master Trust Structures [member] Member ck0001649373:MasterTrustStructuresMember
2976 Other Securitisation Structures [member] Member ck0001649373:OtherSecuritisationStructuresMember
2977 Disclosure of securitisations and covered bonds [line items] LineItems ck0001649373:DisclosureOfSecuritisationsAndCoveredBondsLineItems
2978 Gross assets Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedInEntitysFinancialStatementsInRelationToStructuredEntities
2979 External notes in issue Concept (Monetary) As Of Credit ifrs-full:NotesAndDebenturesIssued
2980 Notes issued to Santander UK plc/subsidiaries as collateral Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
2981 held by the Santander UK group Concept (Monetary) As Of Credit ck0001649373:NotesInIssueHeldByGroup
2982 Total securitisation and covered bond programmes (see Note 28) Concept (Monetary) As Of Credit ck0001649373:SecuritisationsAndCoveredBond
2983 1227 - Disclosure - Securitisations and Covered Bonds - Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSecuritisationsAndCoveredBondsSummaryOfIssuancesAndRedemptionsOfSecuritisationAndCoveredBondProgramme
2984 Issuances And Redemptions Of Securitisation And Covered Bond [table] Table

*

*

 ck0001649373:IssuancesAndRedemptionsOfSecuritisationAndCoveredBondTable
2985 Securitization By Program Name [axis] Axis ck0001649373:SecuritizationByProgramNameAxis
2986 Securitization By Program Name [domain] Member ck0001649373:SecuritizationByProgramNameDomain
2987 Internal [member] Member ck0001649373:InternalMember
2988 External [member] Member ck0001649373:ExternalMember
2989 Type Of Securitisation [axis] Axis ck0001649373:TypeOfSecuritisationAxis
2990 Type Of Securitisation [domain] Member ck0001649373:TypeOfSecuritisationDomain
2991 Master Trust Structures [member] Member ck0001649373:MasterTrustStructuresMember
2992 Other Securitisation Structures [member] Member ck0001649373:OtherSecuritisationStructuresMember
2993 Covered Bond Programme [member] Member ck0001649373:CoveredBondProgrammeMember
2994 Securitisation By Company Name [axis] Axis ck0001649373:SecuritisationByCompanyNameAxis
2995 Securitisation By Company Name [domain] Member ck0001649373:SecuritisationByCompanyNameDomain
2996 Holmes [member] Member ck0001649373:HolmesMember
2997 Fosse [member] Member ck0001649373:FosseMember
2998 Motor [member] Member ck0001649373:MotorMember
2999 Auto ABS UK Loans [member] Member ck0001649373:AutoABSUKLoansMember
3000 Issuances And Redemptions Of Securitisation And Covered Bond [Line items] LineItems ck0001649373:IssuancesAndRedemptionsOfSecuritisationAndCoveredBondLineItems
3001 Internal and external issuances Concept (Monetary) For Period Credit ck0001649373:MortgageBackedNotesIssued
3002 Internal and external redemptions Concept (Monetary) For Period Debit ck0001649373:MortgageBackedSecuritiesRedeemed
3003 1228 - Disclosure - Securitisations and Covered Bonds - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSecuritisationsAndCoveredBondsAdditionalInformation
3004 Gross assets securitised [table] Table

*

*

 ck0001649373:GrossAssetsSecuritisedTable
3005 Securitisation By Company Name [axis] Axis ck0001649373:SecuritisationByCompanyNameAxis
3006 Securitisation By Company Name [domain] Member ck0001649373:SecuritisationByCompanyNameDomain
3007 Holmes [member] Member ck0001649373:HolmesMember
3008 Fosse [member] Member ck0001649373:FosseMember
3009 Langton [member] Member ck0001649373:LangtonMember
3010 Disclosure of gross asset securitised [line items] LineItems ck0001649373:DisclosureOfGrossAssetSecuritisedLineItems
3011 Beneficial interest in residential mortgage loans Concept (Monetary) As Of Debit ck0001649373:BeneficialInterestInMortgages
3012 Cash deposits Concept (Monetary) As Of Credit ck0001649373:CashDeposit
3013 1229 - Disclosure - Transfers of Financial Assets Not Qualifying for Derecognition - Carrying Amount of Financial Assets that Did Not Qualify for Derecognition and their Associated Financial Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransfersOfFinancialAssetsNotQualifyingForDerecognitionCarryingAmountOfFinancialAssetsThatDidNotQualifyForDerecognitionAndTheirAssociatedFinancialLiabilities
3014 Disclosure of continuing involvement in derecognised financial assets [table] Table

*

*

 ifrs-full:DisclosureOfContinuingInvolvementInDerecognisedFinancialAssetsTable
3015 Continuing involvement in derecognised financial assets by type of transfer [axis] Axis ifrs-full:ContinuingInvolvementInDerecognisedFinancialAssetsByTypeOfTransferAxis
3016 Types of transfer [member] Member ifrs-full:TypesOfTransferMember
3017 Sale and Repurchase Agreements [member] Member ck0001649373:SaleAndRepurchaseAgreementsMember
3018 Securities lending agreements [member] Member ck0001649373:SecuritiesLendingAgreementsMember
3019 Securitisations [member] Member ifrs-full:SecuritisationsMember
3020 Disclosure of continuing involvement in derecognised financial assets [line items] LineItems ifrs-full:DisclosureOfContinuingInvolvementInDerecognisedFinancialAssetsLineItems
3021 Carrying amount of financial assets not derecognised in their entirety Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsRepresentingContinuingInvolvementInDerecognisedFinancialAssets
3022 Carrying amount of associated financial liabilities Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesRepresentingContinuingInvolvementInDerecognisedFinancialAssets
3023 1230 - Disclosure - Reverse Repurchase Agreements - Non Trading - Summary of Reverse Repurchase Agreements - Non Trading (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureReverseRepurchaseAgreementsNonTradingSummaryOfReverseRepurchaseAgreementsNonTrading
3024 Disclosure of reserve repurchase agreements non-trading [table] Table

*

*

 ck0001649373:DisclosureOfReserveRepurchaseAgreementsNontradingTable
3025 Types of agreement [axis] Axis ck0001649373:TypesOfAgreementAxis
3026 Types of agreement [domain] Member ck0001649373:TypesOfAgreementDomain
3027 Agreements with banks [member] Member ck0001649373:AgreementsWithBanksMember
3028 Agreements with customers [member] Member ck0001649373:AgreementsWithCustomersMember
3029 Disclosure of reserve repurchase agreements non-trading [line items] LineItems ck0001649373:DisclosureOfReserveRepurchaseAgreementsNontradingLineItems
3030 Reverse repurchase agreements-non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
3031 1231 - Disclosure - Other Financial Assets At Amortised Cost - Summary of Other Financial Assets at Amortised Cost (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialAssetsAtAmortisedCostSummaryOfOtherFinancialAssetsAtAmortisedCost
3032 Financial Assets At Fair Value Through Profit Or Loss [table] Table

*

*

 ck0001649373:FinancialAssetsAtFairValueThroughProfitOrLossTable
3033 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
3034 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
3035 Other Financial Assets [member] Member ck0001649373:OtherFinancialAssets1Member
3036 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
3037 Assets [member] Member ifrs-full:ClassesOfAssetsMember
3038 Asset backed securities [member] Member ck0001649373:AssetBackedSecuritiesMember
3039 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
3040 Financial assets at amortised cost [line items] LineItems ck0001649373:OtherFinancialAssetsAtAmortisedCostLineItems
3041 Financial assets at amortised cost Concept (Monetary) As Of Debit ck0001649373:OtherFinancialAssetsAtAmortisedCost
3042 1232 - Disclosure - Financial Assets At Fair Value Through Other Comprehensive Income - Summary of Financial Assets at Fair Value Through Other Comprehensive Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeSummaryOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
3043 Implied Table Table

*

*

 implied:Table
3044 Financial assets at fair value through other comprehensive income [abstract] Abstract ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeAbstract
3045 Debt securities Concept (Monetary) As Of Debit ck0001649373:DebtSecuritiesClassifiedAsFairValueThroughOtherComprehensiveIncome
3046 Loans and advances to customers Concept (Monetary) As Of Debit ck0001649373:LoansAndAdvanceToCustomersClassifiedAsFairValueThroughOtherComprehensiveIncome
3047 Financial assets at fair value through other comprehensive income Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
3048 1233 - Disclosure - Financial Investments - Summary of Financial Investments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInvestmentsSummaryOfFinancialInvestments
3049 Disclosure of financial investments [table] Table

*

*

 ck0001649373:DisclosureOfFinancialInvestmentsTable
3050 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
3051 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
3052 Available-for-sale [member] Member ifrs-full:FinancialAssetsAvailableforsaleCategoryMember
3053 Held-to-maturity debt securities [member] Member ifrs-full:HeldtomaturityInvestmentsCategoryMember
3054 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3055 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3056 Asset-backed Securities [member] Member ck0001649373:AssetBackedSecuritiesAssetsMember
3057 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
3058 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
3059 Disclosure of financial investments [line items] LineItems ck0001649373:DisclosureOfFinancialInvestmentsLineItems
3060 Financial investments Concept (Monetary) As Of Debit ck0001649373:FinancialInvestments
3061 1234 - Disclosure - Interests in Other Entities - Schedule of Interests in Other Entities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesScheduleOfInterestsInOtherEntities
3062 Implied Table Table

*

*

 implied:Table
3063 Disclosure of interest in other entities [abstract] Abstract ck0001649373:DisclosureOfInterestInOtherEntitiesAbstract
3064 Joint ventures Concept (Monetary) As Of Debit ifrs-full:InvestmentsInJointVentures
3065 Total Concept (Monetary) As Of Debit ifrs-full:InvestmentsInSubsidiariesJointVenturesAndAssociates
3066 1235 - Disclosure - Interests In Other Entities - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesAdditionalInformation
3067 Disclosure of subsidiaries [table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
3068 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3069 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3070 Santander UK Operations Ltd [member] Member ck0001649373:SantanderUkOperationsLtdMember
3071 Santander UK Technology Ltd [member] Member ck0001649373:SantanderUkTechnologyLtdMember
3072 Produban servicios informaticos generales SI [member] Member ck0001649373:ProdubanServiciosInformaticosGeneralesSlMember
3073 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3074 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3075 Subsidiaries with material non-controlling interests [member] Member ifrs-full:SubsidiariesWithMaterialNoncontrollingInterestsMember
3076 Non-adjusting events after reporting period [axis] Axis ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
3077 Non-adjusting Events After Reporting Period [member] Member ifrs-full:NonadjustingEventsMember
3078 Events After Reporting Period [member] Member ck0001649373:EventsAfterReportingPeriodMember
3079 Disclosure of subsidiaries [line items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
3080 Percentage of ownership in subsidiaries Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInSubsidiary
3081 Cash consideration Concept (Monetary) For Period Credit ifrs-full:ConsiderationPaidReceived
3082 1236 - Disclosure - Interests in Other Entities - Schedule of Subsidiaries With Significant Non-Controlling Interests (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesScheduleOfSubsidiariesWithSignificantNonControllingInterests
3083 Disclosure of subsidiaries [table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
3084 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3085 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3086 Subsidiaries with material non-controlling interests [member] Member ifrs-full:SubsidiariesWithMaterialNoncontrollingInterestsMember
3087 Disclosure of subsidiaries [line items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
3088 Profit attributable to non-controlling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
3089 Accumulated non-controlling interests of the subsidiary Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
3090 Dividends paid to non-controlling interests Concept (Monetary) For Period Credit ifrs-full:DividendsPaidToNoncontrollingInterests
3091 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
3092 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
3093 Profit for the year Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
3094 Total comprehensive income for the year Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
3095 1237 - Disclosure - Interests In Other Entities - Interests in Consolidated Structured Entities - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesInterestsInConsolidatedStructuredEntitiesAdditionalInformation
3096 Disclosure of information about unconsolidated subsidiaries [table] Table

*

*

 ifrs-full:DisclosureOfInformationAboutUnconsolidatedSubsidiariesTable
3097 Consolidated structured entities [axis] Axis ifrs-full:ConsolidatedStructuredEntitiesAxis
3098 Entity's total for consolidated structured entities [member] Member ifrs-full:EntitysTotalForConsolidatedStructuredEntitiesMember
3099 Santander UK Foundation Limited [member] Member ck0001649373:SantanderUkFoundationLimitedMember
3100 Disclosure of information about consolidated structured entities [line items] LineItems ifrs-full:DisclosureOfInformationAboutConsolidatedStructuredEntitiesLineItems
3101 Third party assets Concept (Monetary) As Of Debit ck0001649373:ThirdPartyAssets
3102 1238 - Disclosure - Interests In Other Entities - Interests in Joint Ventures - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesInterestsInJointVenturesAdditionalInformation
3103 Disclosure of joint ventures [table] Table

*

*

 ifrs-full:DisclosureOfJointVenturesTable
3104 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
3105 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
3106 Joint ventures [member] Member ifrs-full:JointVenturesMember
3107 Disclosure of joint ventures [line items] LineItems ifrs-full:DisclosureOfJointVenturesLineItems
3108 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfContinuingOperationsOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
3109 Carrying value of interest in joint venture Concept (Monetary) As Of Debit ifrs-full:InvestmentsInJointVentures
3110 Commitments and contingent liabilities Concept (Monetary) As Of Credit ck0001649373:CommitmentsAndContingencies1
3111 1239 - Disclosure - Interests In Other Entities - Interests in Unconsolidated Structured Entities - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesInterestsInUnconsolidatedStructuredEntitiesAdditionalInformation
3112 Disclosure of information about unconsolidated subsidiaries [table] Table

*

*

 ifrs-full:DisclosureOfInformationAboutUnconsolidatedSubsidiariesTable
3113 Unconsolidated structured entities [axis] Axis ifrs-full:UnconsolidatedStructuredEntitiesAxis
3114 Entity's total for unconsolidated structured entities [member] Member ifrs-full:EntitysTotalForUnconsolidatedStructuredEntitiesMember
3115 Santander (UK) Common Investment Fund [member] Member ck0001649373:SantanderUkCommonInvestmentFundMember
3116 Abbey National Capital Trust I [member] Member ck0001649373:AbbeyNationalCapitalTrustiMember
3117 Abbey National Capital LP I [member] Member ck0001649373:AbbeyNationalCapitalLpMember
3118 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3119 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3120 Entities with Joint Control or Significant Influence over Entity [Member] Member ifrs-full:JointControlOrSignificantInfluenceMember
3121 Disclosure of information about unconsolidated subsidiaries [line items] LineItems ifrs-full:DisclosureOfInformationAboutUnconsolidatedSubsidiariesLineItems
3122 Defined benefit assets and obligations Concept (Monetary) As Of Debit ifrs-full:AssetsOfBenefitPlan
3123 Name of subsidiary Concept (Text/String) For Period ifrs-full:NameOfSubsidiary
3124 Ownership interest in trust preferred entities by Santander UK plc Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInSubsidiary
3125 Non-cumulative trust preferred securities issued Concept (Monetary) For Period Credit ck0001649373:NoncumulativeTrustPreferredSecuritiesIssued
3126 Non-cumulative trust preferred securities interest rate Concept (Percent) For Period ck0001649373:NoncumulativeTrustPreferredSecuritiesInterestRate
3127 Number of credit protection vehicles Concept (Decimal) For Period ck0001649373:NumberOfCreditProtectionVehicles
3128 Credit Linked Notes issued Concept (Monetary) As Of Credit ck0001649373:CreditLinkedNotesIssued
3129 1240 - Disclosure - Intangible Assets - Schedule of Goodwill (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureIntangibleAssetsScheduleOfGoodwill
3130 Disclosure of Goodwill [table] Table

*

*

 ck0001649373:DisclosureOfGoodwillTable
3131 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
3132 Carrying amount [member] Member ifrs-full:CarryingAmountMember
3133 Cost [member] Member ifrs-full:GrossCarryingAmountMember
3134 Accumulated Impairment [member] Member ifrs-full:AccumulatedImpairmentMember
3135 Disclosure of goodwill [line items] LineItems ck0001649373:DisclosureOfGoodwillLineItems
3136 Carrying amount Concept (Monetary) As Of Debit ifrs-full:Goodwill
3137 1241 - Disclosure - Intangible Assets - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureIntangibleAssetsAdditionalInformation
3138 Implied Table Table

*

*

 implied:Table
3139 Disclosure of detailed information about intangible assets [abstract] Abstract ifrs-full:DisclosureOfIntangibleAssetsAbstract
3140 Goodwill impairment recognised Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossGoodwill
3141 Increase/(decrease) in discount rate percentage Concept (Percent) For Period ck0001649373:IncreaseDecreaseInDiscountRateAppliedToCashFlowProjections
3142 Discount rate percentage Concept (Percent) As Of ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
3143 1242 - Disclosure - Intangible Assets - Schedule of Goodwill for Cash Generating Units (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureIntangibleAssetsScheduleOfGoodwillForCashGeneratingUnits
3144 Disclosure of information for cash-generating units [table] Table

*

*

 ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesTable
3145 Individual assets or cash-generating units [axis] Axis ifrs-full:IndividualAssetsOrCashgeneratingUnitsAxis
3146 Entity's total for individual assets or cash-generating units [member] Member ifrs-full:EntitysTotalForIndividualAssetsOrCashgeneratingUnitsMember
3147 Personal Financial Services [member] Member ck0001649373:PersonalFinancialServicesMember
3148 Private Banking [member] Member ck0001649373:PrivateBankingMember
3149 Other [member] Member ck0001649373:OtherMember
3150 Disclosure of information for cash-generating units [line items] LineItems ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesLineItems
3151 Goodwill Concept (Monetary) As Of Debit ifrs-full:Goodwill
3152 Discount rate Concept (Percent) As Of ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
3153 Growth rate Concept (Percent) As Of ifrs-full:DescriptionOfGrowthRateUsedToExtrapolateCashFlowProjections
3154 1243 - Disclosure - Intangible Assets - Schedule of Goodwill for Cash Generating Units (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureIntangibleAssetsScheduleOfGoodwillForCashGeneratingUnitsParenthetical
3155 Implied Table Table

*

*

 implied:Table
3156 Disclosure of information for cash-generating units [abstract] Abstract ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAbstract
3157 Terminal growth rate Concept (Percent) For Period ck0001649373:TerminalGrowthRateUsedToExtrapolateCashFlowProjections
3158 1244 - Disclosure - Intangible Assets - Schedule of Other Intangibles (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureIntangibleAssetsScheduleOfOtherIntangibles
3159 Disclosure of detailed information about intangible assets [table] Table

*

*

 ifrs-full:DisclosureOfIntangibleAssetsTable
3160 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
3161 Carrying amount [member] Member ifrs-full:CarryingAmountMember
3162 Cost [member] Member ifrs-full:GrossCarryingAmountMember
3163 Accumulated amortisation / impairment [member] Member ck0001649373:AccumulatedAmortizationAndImpairmentMember
3164 Disclosure of detailed information about intangible assets [line items] LineItems ifrs-full:DisclosureOfIntangibleAssetsLineItems
3165 Beginning balance Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
3166 Additions Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
3167 Write offs Concept (Monetary) For Period Credit ifrs-full:RetirementsIntangibleAssetsOtherThanGoodwill
3168 Disposals Concept (Monetary) For Period Credit ifrs-full:DisposalsIntangibleAssetsOtherThanGoodwill
3169 Charge Concept (Monetary) For Period ifrs-full:AmortisationIntangibleAssetsOtherThanGoodwill
3170 Sales Concept (Monetary) For Period Credit ck0001649373:SalesIntangibleAssetsOtherThanGoodwill
3171 Impairment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsOtherThanGoodwill
3172 Ending balance Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
3173 1245 - Disclosure - Trading Liabilities - Schedule of Trading Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTradingLiabilitiesScheduleOfTradingLiabilities
3174 Disclosure of financial liabilities held for trading [table] Table

*

*

 ck0001649373:DisclosureOfFinancialLiabilitiesHeldForTradingTable
3175 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3176 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3177 Securities Sold Under Repurchase Agreements [member] Member ck0001649373:SecuritiesSoldUnderRepurchaseAgreementsMember
3178 Short Positions in Securities and Unsettled Trades [member] Member ck0001649373:ShortPositionsInSecuritiesAndUnsettledTradesMember
3179 Cash Collateral [member] Member ck0001649373:CashCollateralMember
3180 Disclosure of financial liabilities held for trading [line items] LineItems ck0001649373:DisclosureOfFinancialLiabilitiesHeldForTradingLineItems
3181 Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
3182 1246 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss - Summary of Other Financial Liabilities at Fair Value Through Profit or Loss (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossSummaryOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
3183 Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [table] Table

*

*

 ck0001649373:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossTable
3184 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3185 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3186 US Dollar Ten Billion Euro commercial paper programmes [member] Member ck0001649373:UsDollarTenBillionEuroCommercialPaperProgrammesMember
3187 US$30bn Euro Medium Term Note Programme [member] Member ck0001649373:USDollarThirtyBillionEuroMediumTermNoteProgrammeMember
3188 Structured Notes Programmes [member] Member ck0001649373:StructuredNotesProgrammesMember
3189 Eurobonds [member] Member ck0001649373:EurobondsMember
3190 Structured Deposits [member] Member ck0001649373:StructuredDepositsMember
3191 Collateral and associated financial guarantees [member] Member ck0001649373:CollateralsAndGuaranteesMember
3192 Repurchase agreements - non trading [member] Member ck0001649373:RepurchaseAgreementsNontradingMember
3193 Disclosure of other financial liabilities at fair value through profit or loss [line items] LineItems ck0001649373:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossLineItems
3194 Other financial liabilities through profit or loss Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
3195 1247 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss - Summary of Other Financial Liabilities at Fair Value Through Profit or Loss (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossSummaryOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossParenthetical
3196 Implied Table Table

*

*

 implied:Table
3197 Disclosure of financial liabilities [abstract] Abstract ifrs-full:DisclosureOfFinancialLiabilitiesAbstract
3198 Financial liabilities designated at fair value through profit or loss Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
3199 Financial liabilities mandatorily at fair value through profit or loss Concept (Monetary) As Of Credit ck0001649373:FinancialLiabilitiesMandatorilyAtFairValueThroughProfitOrLoss
3200 1248 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossAdditionalInformation
3201 Implied Table Table

*

*

 implied:Table
3202 Other financial liabilities at fair value through profit or loss [abstract] Abstract ck0001649373:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLossAbstract
3203 Net gain (loss) on financial liabilities designated at fair value, attributable to changes in credit risk Concept (Monetary) For Period Credit ifrs-full:ChangesInFairValueOfFinancialLiabilityAttributableToChangesInCreditRiskOfLiability
3204 Accumulated gain (loss) on financial liabilities designated at fair value, attributable to changes in credit risk Concept (Monetary) As Of Credit ifrs-full:AccumulatedChangesInFairValueOfFinancialLiabilityAttributableToChangesInCreditRiskOfLiability
3205 Difference between carrying amount of financial liability and amount contractually required to pay at maturity to holder of obligation Concept (Monetary) As Of ifrs-full:DifferenceBetweenCarryingAmountOfFinancialLiabilityAndAmountContractuallyRequiredToPayAtMaturityToHolderOfObligation
3206 1249 - Disclosure - Deposits by Customers - Schedule of Deposits by Customers (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDepositsByCustomersScheduleOfDepositsByCustomers
3207 Disclosure of deposits from customers [table] Table

*

*

 ck0001649373:DisclosureOfDepositsFromCustomersTable
3208 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3209 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3210 Current and Demand Accounts - [member] Member ck0001649373:CurrentAndDemandAccountsMember
3211 Savings Accounts [member] Member ck0001649373:SavingsAccountsMember
3212 Time Deposits [member] Member ck0001649373:TimeDepositsMember
3213 Amounts Due to Fellow Banco Santander Subsidiaries and Joint Ventures - [member] Member ck0001649373:AmountsDueToFellowBancoSantanderSubsidiariesAndJointVenturesMember
3214 Disclosure of deposits from customers [line items] LineItems ck0001649373:DisclosureOfDepositsFromCustomersLineItems
3215 Deposits from customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
3216 1250 - Disclosure - Deposits by Customers - Schedule of Deposits by Customers (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDepositsByCustomersScheduleOfDepositsByCustomersParenthetical
3217 Disclosure of deposits from customers [table] Table

*

*

 ck0001649373:DisclosureOfDepositsFromCustomersTable
3218 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3219 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3220 Equity Index Linked Deposits [member] Member ck0001649373:EquityIndexLinkedDepositsMember
3221 Disclosure of deposits from customers [line items] LineItems ck0001649373:DisclosureOfDepositsFromCustomersLineItems
3222 Deposits from customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
3223 Capital amount guaranteed or protected Concept (Monetary) As Of Credit ck0001649373:CapitalAmountGuaranteedOrProtectedInRespectOfEquityIndexLinkedDeposits
3224 Capital amount of return guaranteed Concept (Monetary) As Of Credit ck0001649373:AmountOfReturnGuaranteedInRespectOfEquityIndexLinkedDeposits
3225 1251 - Disclosure - Deposits by Banks - Schedule of Deposits by Banks (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDepositsByBanksScheduleOfDepositsByBanks
3226 Disclosure Of Deposits From Banks [table] Table

*

*

 ck0001649373:DisclosureOfDepositsFromBanksTable
3227 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3228 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3229 Items in Course of Transmission [member] Member ck0001649373:ItemsInCourseOfTransmissionMember
3230 Deposits Held as Collateral [member] Member ck0001649373:DepositsHeldAsCollateralMember
3231 Other Deposits [member] Member ck0001649373:OtherDepositsMember
3232 Disclosure of deposits from banks [line items] LineItems ck0001649373:DisclosureOfDepositsFromBanksLineItems
3233 Deposits from banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
3234 1252 - Disclosure - Deposits by Banks - Schedule of Deposits by Banks (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDepositsByBanksScheduleOfDepositsByBanksParenthetical
3235 Implied Table Table

*

*

 implied:Table
3236 Disclosure of deposits from banks [abstract] Abstract ck0001649373:DisclosureOfDepositsFromBanksAbstract
3237 Drawdown from TFS Concept (Monetary) As Of Credit ck0001649373:DrawdownFromTermFundingScheme
3238 1253 - Disclosure - Repurchase Agreements - Non Trading - Summary of Repurchase Agreements Non Trading (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRepurchaseAgreementsNonTradingSummaryOfRepurchaseAgreementsNonTrading
3239 Disclosure Of Repurchase Agreements [table] Table

*

*

 ck0001649373:DisclosureOfRepurchaseAgreementsTable
3240 Types of agreement [axis] Axis ck0001649373:TypesOfAgreementAxis
3241 Types of agreement [domain] Member ck0001649373:TypesOfAgreementDomain
3242 Agreements with banks [member] Member ck0001649373:AgreementsWithBanksMember
3243 Agreements with customers [member] Member ck0001649373:AgreementsWithCustomersMember
3244 Disclosure Of Repurchase Agreements [line items] LineItems ck0001649373:DisclosureOfRepurchaseAgreementsLineItems
3245 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
3246 1254 - Disclosure - Debt Securities In Issue - Summary of Debt Securities in Issue (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDebtSecuritiesInIssueSummaryOfDebtSecuritiesInIssue
3247 Debt Securities in Issue [Table] Table

*

*

 ck0001649373:DebtSecuritiesInIssueTable
3248 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3249 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3250 Medium Term Notes [member] Member ck0001649373:MediumTermNotes1Member
3251 Euro 35bn Global Covered Bond Programme [member] Member ck0001649373:EuroThirtyFiveBillionGlobalCoveredBondProgrammeMember
3252 Certificates of Deposit [member] Member ck0001649373:CertificateOfDepositMember
3253 Credit Linked Note [member] Member ck0001649373:CreditLinkedNoteMember
3254 Securitisation Programmes [member] Member ck0001649373:SecuritisationProgrammesMember
3255 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3256 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3257 US$30bn Euro Medium Term Note Programme [member] Member ck0001649373:USDollarThirtyBillionEuroMediumTermNoteProgrammeMember
3258 Euro 30bn Euro Medium Term Note Programme [member] Member ck0001649373:EuroThirtyBillionEuroMediumTermNoteProgrammeMember
3259 US SEC - Registered - Santander UK Group Holdings Plc [member] Member ck0001649373:USSECRegisteredSantanderUKGroupHoldingsPlcMember
3260 US SEC - Registered - Santander UK Plc [member] Member ck0001649373:USSECRegisteredSantanderUKPlcMember
3261 US$20bn Commercial Paper Programmes [member] Member ck0001649373:USDollarTwentyBillionCommercialPaperProgrammeMember
3262 Debt securities in issue [line items] LineItems ck0001649373:DebtSecuritiesInIssueLineItems
3263 Debt Securities Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
3264 Credit Linked Notes Concept (Monetary) As Of Credit ck0001649373:CreditLinkedNotesIssued
3265 1255 - Disclosure - Debt Securities In Issue - Summary of Debt Securities in Issue (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDebtSecuritiesInIssueSummaryOfDebtSecuritiesInIssueParenthetical
3266 Debt Securities in Issue [Table] Table

*

*

 ck0001649373:DebtSecuritiesInIssueTable
3267 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3268 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3269 Medium Term Notes [member] Member ck0001649373:MediumTermNotes1Member
3270 Euro 35bn Global Covered Bond Programme [member] Member ck0001649373:EuroThirtyFiveBillionGlobalCoveredBondProgrammeMember
3271 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3272 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3273 US$30bn Euro Medium Term Note Programme [member] Member ck0001649373:USDollarThirtyBillionEuroMediumTermNoteProgrammeMember
3274 Euro 30bn Euro Medium Term Note Programme [member] Member ck0001649373:EuroThirtyBillionEuroMediumTermNoteProgrammeMember
3275 US$20bn Commercial Paper Programmes [member] Member ck0001649373:USDollarTwentyBillionCommercialPaperProgrammeMember
3276 Debt securities in issue [line items] LineItems ck0001649373:DebtSecuritiesInIssueLineItems
3277 Notional amount Concept (Monetary) As Of ifrs-full:NotionalAmount
3278 1256 - Disclosure - Debt Securities In Issue - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureDebtSecuritiesInIssueAdditionalInformation
3279 Debt Securities in Issue [Table] Table

*

*

 ck0001649373:DebtSecuritiesInIssueTable
3280 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3281 Equity [member] Member ifrs-full:EquityMember
3282 PSA Finance UK Limited [member] Member ck0001649373:PSAFinanceUKLimitedMember
3283 Debt securities in issue [line items] LineItems ck0001649373:DebtSecuritiesInIssueLineItems
3284 Percentage of losses in portfolio having credit protection Concept (Percent) For Period ck0001649373:PercentageOfLossesInPortfolioHavingCreditProtection
3285 1257 - Disclosure - Subordinated Liabilities - Schedule of Subordinated Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesScheduleOfSubordinatedLiabilities
3286 Implied Table Table

*

*

 implied:Table
3287 Disclosure of Subordinated Liabilities [abstract] Abstract ck0001649373:DisclosureOfSubordinatedLiabilitiesAbstract
3288 £325m Sterling Preference Shares Concept (Monetary) As Of Credit ck0001649373:SterlingPreferenceShares
3289 £175m Fixed/Floating Rate Tier One Preferred Income Capital Securities Concept (Monetary) As Of Credit ck0001649373:FixedFloatingRateTierOnePreferredIncomeCapitalSecurities
3290 Undated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:UndatedSubordinatedLiabilities
3291 Dated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:DatedSubordinatedLiabilities
3292 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
3293 1258 - Disclosure - Subordinated Liabilities - Schedule of Subordinated Liabilities (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesScheduleOfSubordinatedLiabilitiesParenthetical
3294 Implied Table Table

*

*

 implied:Table
3295 Disclosure of Subordinated Liabilities [abstract] Abstract ck0001649373:DisclosureOfSubordinatedLiabilitiesAbstract
3296 325m Sterling Preference Shares, Notional amount Concept (Monetary) As Of ck0001649373:SterlingPreferenceSharesNotionalAmount
3297 175m Fixed/Floating Rate Tier One Preferred Income Capital Securities, Notional amount Concept (Monetary) As Of ck0001649373:FixedFloatingRateTierOnePreferredIncomeCapitalSecuritiesNotionalAmount
3298 1259 - Disclosure - Subordinated Liabilities - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesAdditionalInformation
3299 Disclosure of Subordinated Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfSubordinatedLiabilitiesTable
3300 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3301 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3302 300m Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001649373:ThreeHundredMillionFixedOrFloatingRateNoncumulativeCallablePreferenceSharesMember
3303 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001649373:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3304 Classes of Share Capital [Axis] Axis ifrs-full:ClassesOfShareCapitalAxis
3305 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
3306 175m Sterling Fixed/Floating Rate Tier One Preferred Income Capital Securities [member] Member ck0001649373:OneSeventyFiveMillionPoundSterlingFixedFloatingRateTierOnePreferredIncomeCapitalSecuritiesMember
3307 10.0625% non-cumulative non-redeemable sterling preference shares [member] Member ck0001649373:TenPointZeroSixTwoFivePercentNoncumulativeNonredeemableSterlingPreferenceSharesMember
3308 10.375% non-cumulative non-redeemable sterling preference shares [member] Member ck0001649373:TenPointThreeSevenFivePercentNoncumulativeNonredeemableSterlingPreferenceSharesMember
3309 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3310 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3311 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
3312 7.125% 30 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointOneTwoFivePercentThirtyYearStepupPerpetualCallableSubordinatedNotesMember
3313 10.0625% Exchangeable Capital Securities [member] Member ck0001649373:TenPointZeroSixTwoFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3314 10.375% exchangeable subordinated capital securities [member] Member ck0001649373:TenPointThreeSevenFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3315 10.125% Subordinated Guaranteed Bond 2023 [member] Member ck0001649373:TenPointOneTwoFivePercentSubordinatedGuaranteedBondTwentyTwentyThreeMember
3316 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3317 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3318 Santander UK Plc [member] Member ck0001649373:SantanderUkPlcMember
3319 Disclosure of subordinated liabilities [line items] LineItems ck0001649373:DisclosureOfSubordinatedLiabilitiesLineItems
3320 Notional amount Concept (Monetary) As Of ck0001649373:FixedFloatingRateTierOnePreferredIncomeCapitalSecuritiesNotionalAmount
3321 Notional amount Concept (Monetary) As Of ck0001649373:StepUpCallablePerpetualReserveCapitalInstrumentsNotionalAmount
3322 Defaults of principal, interest or other breaches with respect to subordinated liabilities Concept (Monetary) As Of Credit ck0001649373:DefaultsOfPrincipalInterestOrOtherBreachesWithRespectToSubordinatedLiabilities
3323 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
3324 Par value per share Concept (Share) As Of ifrs-full:ParValuePerShare
3325 1260 - Disclosure - Subordinated Liabilities - Summary of Undated Subordinated Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfUndatedSubordinatedLiabilities
3326 Disclosure of Subordinated Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfSubordinatedLiabilitiesTable
3327 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3328 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3329 10.0625% Exchangeable Capital Securities [member] Member ck0001649373:TenPointZeroSixTwoFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3330 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
3331 7.125% 30 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointOneTwoFivePercentThirtyYearStepupPerpetualCallableSubordinatedNotesMember
3332 Disclosure of subordinated liabilities [line items] LineItems ck0001649373:DisclosureOfSubordinatedLiabilitiesLineItems
3333 Undated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:UndatedSubordinatedLiabilities
3334 First call date Concept (Text/String) For Period ck0001649373:InitialCallDateOfUndatedSubordinatedLiabilities
3335 1261 - Disclosure - Subordinated Liabilities - Summary of Undated Subordinated Liabilities (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfUndatedSubordinatedLiabilitiesParenthetical
3336 Disclosure of Subordinated Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfSubordinatedLiabilitiesTable
3337 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3338 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3339 10.0625% Exchangeable Capital Securities [member] Member ck0001649373:TenPointZeroSixTwoFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3340 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
3341 7.125% 30 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001649373:SevenPointOneTwoFivePercentThirtyYearStepupPerpetualCallableSubordinatedNotesMember
3342 Disclosure of subordinated liabilities [line items] LineItems ck0001649373:DisclosureOfSubordinatedLiabilitiesLineItems
3343 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
3344 Notes maturity, year Concept (xbrli:durationItemType) For Period ck0001649373:BorrowingsMaturityPeriod
3345 Maturity period Concept (Text/String) For Period ifrs-full:BorrowingsMaturity
3346 1262 - Disclosure - Subordinated Liabilities - Summary of Dated Subordinated Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfDatedSubordinatedLiabilities
3347 Disclosure of Subordinated Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfSubordinatedLiabilitiesTable
3348 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3349 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3350 10.125% Subordinated Guaranteed Bond 2023 [member] Member ck0001649373:TenPointOneTwoFivePercentSubordinatedGuaranteedBondTwentyTwentyThreeMember
3351 9.625% Subordinated Notes 2023 [member] Member ck0001649373:NinePointSixTwoFivePercentSubordinatedNotesTwentyTwentyThreeMember
3352 5% Subordinated Notes 2023 [member] Member ck0001649373:FivePercentSubordinatedNotesTwentyTwentyThreeMember
3353 4.75% Subordinated Notes 2025 [member] Member ck0001649373:FourPointSevenFivePercentSubordinatedNotesTwentyTwentyFiveMember
3354 7.95% Subordinated Notes 2029 [member] Member ck0001649373:SevenPointNineFivePercentSubordinatedNotesTwentyTwentyNineMember
3355 6.50% Subordinated Notes 2030 [member] Member ck0001649373:SixPointFivePercentSubordinatedNotesTwentyThirtyMember
3356 8.963% Subordinated Notes 2045 [member] Member ck0001649373:EightPointNineSixThreePercentNotesTwentyFortyFiveMember
3357 5.875% Subordinated Notes 2031 [member] Member ck0001649373:FivePointEightSevenFivePercentSubordinatedNotesTwentyThirtyOneMember
3358 5.625% Subordinated Notes 2045 [member] Member ck0001649373:FivePointSixTwoFivePercentSubordinatedNotesTwentyFortyFiveMember
3359 Disclosure of subordinated liabilities [line items] LineItems ck0001649373:DisclosureOfSubordinatedLiabilitiesLineItems
3360 Dated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:DatedSubordinatedLiabilities
3361 Maturity period Concept (Text/String) For Period ifrs-full:BorrowingsMaturity
3362 1263 - Disclosure - Subordinated Liabilities - Summary of Dated Subordinated Liabilities (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfDatedSubordinatedLiabilitiesParenthetical
3363 Disclosure of Subordinated Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfSubordinatedLiabilitiesTable
3364 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3365 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3366 10.125% Subordinated Guaranteed Bond 2023 [member] Member ck0001649373:TenPointOneTwoFivePercentSubordinatedGuaranteedBondTwentyTwentyThreeMember
3367 9.625% Subordinated Notes 2023 [member] Member ck0001649373:NinePointSixTwoFivePercentSubordinatedNotesTwentyTwentyThreeMember
3368 5% Subordinated Notes 2023 [member] Member ck0001649373:FivePercentSubordinatedNotesTwentyTwentyThreeMember
3369 4.75% Subordinated Notes 2025 [member] Member ck0001649373:FourPointSevenFivePercentSubordinatedNotesTwentyTwentyFiveMember
3370 7.95% Subordinated Notes 2029 [member] Member ck0001649373:SevenPointNineFivePercentSubordinatedNotesTwentyTwentyNineMember
3371 6.50% Subordinated Notes 2030 [member] Member ck0001649373:SixPointFivePercentSubordinatedNotesTwentyThirtyMember
3372 8.963% Subordinated Notes 2045 [member] Member ck0001649373:EightPointNineSixThreePercentNotesTwentyFortyFiveMember
3373 5.875% Subordinated Notes 2031 [member] Member ck0001649373:FivePointEightSevenFivePercentSubordinatedNotesTwentyThirtyOneMember
3374 5.625% Subordinated Notes 2045 [member] Member ck0001649373:FivePointSixTwoFivePercentSubordinatedNotesTwentyFortyFiveMember
3375 Disclosure of subordinated liabilities [line items] LineItems ck0001649373:DisclosureOfSubordinatedLiabilitiesLineItems
3376 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
3377 Notional amount Concept (Monetary) As Of Credit ck0001649373:SubordinatedNotesNotionalAmount
3378 1264 - Disclosure - Provisions - Summary of Provisions Reconciliation (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureProvisionsSummaryOfProvisionsReconciliation
3379 Disclosure of other provisions [table] Table

*

*

 ifrs-full:DisclosureOfOtherProvisionsTable
3380 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3381 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3382 PPI [member] Member ck0001649373:PPIMember
3383 Other products [member] Member ck0001649373:OtherProductsMember
3384 FSCS and Bank Levy [member] Member ck0001649373:FSCSAndBankLevyMember
3385 Vacant Property [member] Member ck0001649373:VacantPropertyMember
3386 Off-Balance Sheet [member] Member ck0001649373:OffBalanceSheetMember
3387 Regulatory and other [member] Member ck0001649373:RegulatoryAndOtherMember
3388 Maturity [axis] Axis ifrs-full:MaturityAxis
3389 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3390 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3391 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
3392 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3393 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Provisions
3394 Reallocation of ECL on off-balance sheet exposures Concept (Monetary) For Period Credit ck0001649373:ReallocationOfExpectedCreditLossOnUndrawnExposuresRelatedToLoanCommitments
3395 Balance on January 1 2018 Concept (Monetary) As Of Credit ck0001649373:ProvisionsOnAdoptionOfIFRS9
3396 Additional provisions Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
3397 Provisions released (see Note 8) Concept (Monetary) For Period Debit ifrs-full:UnusedProvisionReversedOtherProvisions
3398 Utilisation Concept (Monetary) For Period Debit ifrs-full:ProvisionUsedOtherProvisions
3399 Other Concept (Monetary) For Period Credit ifrs-full:NewProvisionsOtherProvisions
3400 Transfers Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesOtherProvisions
3401 Ending balance Concept (Monetary) As Of Credit ifrs-full:Provisions
3402 To be settled: Abstract ck0001649373:ToBeSettledAbstract
3403 Ending balance Concept (Monetary) As Of Credit ifrs-full:Provisions
3404 1265 - Disclosure - Provisions - Summary of Provisions Reconciliation (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureProvisionsSummaryOfProvisionsReconciliationParenthetical
3405 Disclosure of other provisions [table] Table

*

*

 ifrs-full:DisclosureOfOtherProvisionsTable
3406 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3407 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3408 FSCS and Bank Levy [member] Member ck0001649373:FSCSAndBankLevyMember
3409 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3410 Other Concept (Monetary) For Period Credit ifrs-full:NewProvisionsOtherProvisions
3411 1266 - Disclosure - Provisions - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureProvisionsAdditionalInformation
3412 Disclosure of other provisions [table] Table

*

*

 ifrs-full:DisclosureOfOtherProvisionsTable
3413 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3414 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3415 PPI [member] Member ck0001649373:PPIMember
3416 Provision for Past Business Review [member] Member ck0001649373:ProvisionForPastBusinessReviewMember
3417 August 2016 FCA Papers [member] Member ck0001649373:AugustTwoThousandSixteenFCAPapersMember
3418 Other products [member] Member ck0001649373:OtherProductsMember
3419 Regulatory Related | Financial Services Compensation Scheme [member] Member ck0001649373:RegulatoryRelatedFinancialServicesCompensationSchemeMember
3420 Regulatory Related Uk Bank Levy [member] Member ck0001649373:RegulatoryRelatedUKBankLevyMember
3421 Compliance with Consumer Credit Act [member] Member ck0001649373:ComplianceWithConsumerCreditActMember
3422 Historical probate and bereavement practices [member] Member ck0001649373:HistoricalProbateAndBereavementPracticesMember
3423 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3424 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3425 Financial Ombudsman Service [member] Member ck0001649373:FinancialOmbudsmanServiceMember
3426 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
3427 Key Drivers PPI [axis] Axis ck0001649373:KeyDriversPPIAxis
3428 Key Drivers PPI [domain] Member ck0001649373:KeyDriversPpiDomain
3429 Plevin redress [member] Member ck0001649373:PlevinRedressMember
3430 Range [axis] Axis ifrs-full:RangeAxis
3431 Ranges [member] Member ifrs-full:RangesMember
3432 Top of Range [member] Member ifrs-full:TopOfRangeMember
3433 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3434 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3435 Provision linked to future claims levels Concept (Monetary) For Period Credit ck0001649373:FutureExpectedProvisionAmount
3436 Impact on the PPI misselling element of provision Concept (Monetary) For Period Debit ck0001649373:SensitivityAnalysisIncreaseDecreaseInProvisionValue
3437 Overturn rate percentage Concept (Percent) For Period ck0001649373:OverturnRatePercentage
3438 Average overturn rate percentage Concept (Percent) For Period ck0001649373:AverageOverturnRatePercentage
3439 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
3440 Additional provision charge Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
3441 Provisions released Concept (Monetary) For Period Debit ifrs-full:UnusedProvisionReversedOtherProvisions
3442 Reduction in amount that FSCS owes to HM Treasury Concept (Monetary) As Of Credit ck0001649373:AmountPayableToHmTreasury
3443 Regulatory costs related to Financial Services Compensation Scheme (FSCS) Concept (Monetary) For Period Debit ck0001649373:ExpensesRelatedToFinancialServicesCompensationScheme
3444 Bank levy rate Concept (Percent) For Period ck0001649373:BankLevyRate
3445 UK Bank Levy Concept (Percent) For Period ck0001649373:UKBankLevyRate
3446 Cost of UK Bank Levy Incurred Concept (Monetary) For Period Debit ck0001649373:ExpensesRelatedToUKBankLevy
3447 Amount paid as UK Bank Levy Concept (Monetary) For Period Debit ck0001649373:UKBankLevyPaid
3448 Additional operational risk losses and restructuring charges Concept (Monetary) For Period Credit ck0001649373:AdditionalProvisionsOtherProvisionsOperationalRiskLossesAndRestructuringCharges
3449 1267 - Disclosure - Provisions - Summary of Key Drivers of PPI Provision Balance and Forecast Assumptions Used in Calculating Provision (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureProvisionsSummaryOfKeyDriversOfPPIProvisionBalanceAndForecastAssumptionsUsedInCalculatingProvision
3450 Disclosure of other provisions [table] Table

*

*

 ifrs-full:DisclosureOfOtherProvisionsTable
3451 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3452 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3453 PPI [member] Member ck0001649373:PPIMember
3454 Key Drivers PPI [axis] Axis ck0001649373:KeyDriversPPIAxis
3455 Key Drivers PPI [domain] Member ck0001649373:KeyDriversPpiDomain
3456 Inbound Complaints [member] Member ck0001649373:InboundComplaintsMember
3457 Outbound Complaints [member] Member ck0001649373:OutboundComplaintsMember
3458 Response Rate to Outbound Contact [member] Member ck0001649373:ResponseRateToOutboundContactMember
3459 Average Uphold Rate Per Claim [member] Member ck0001649373:AverageUpholdRatePerClaimMember
3460 Average Redress Per Claim [member] Member ck0001649373:AverageRedressPerClaimMember
3461 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3462 Cumulative to 31 December 2018 Concept (Percent) For Period ck0001649373:ProvisionCumulativeToYearEndRate
3463 Cumulative to 31 December 2018 Concept (Integer) For Period ck0001649373:ProvisionCumulativeToYearEndNumber
3464 Cumulative to 31 December 2018 Concept (Monetary) For Period Credit ck0001649373:ProvisionCumulativeToYearEndAmount
3465 Future expected (unaudited) Concept (Percent) For Period ck0001649373:FutureExpectedProvisionRate
3466 Future expected (unaudited) Concept (Integer) For Period ck0001649373:FutureExpectedProvisionNumber
3467 Future expected (unaudited) Concept (Monetary) For Period Credit ck0001649373:FutureExpectedProvisionAmount
3468 Sensitivity analysis rate Concept (Percent) For Period ck0001649373:SensitivityAnalysisRate
3469 Sensitivity analysis number Concept (Integer) For Period ck0001649373:SensitivityAnalysisNumber
3470 Sensitivity analysis amount Concept (Monetary) For Period Debit ck0001649373:SensitivityAnalysisAmount
3471 Sensitivity analysis increase/decrease in provision Concept (Monetary) For Period Debit ck0001649373:SensitivityAnalysisIncreaseDecreaseInProvisionValue
3472 1268 - Disclosure - Provisions - Summary of Key Drivers of PPI Provision Balance and Forecast Assumptions Used in Calculating Provision (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureProvisionsSummaryOfKeyDriversOfPPIProvisionBalanceAndForecastAssumptionsUsedInCalculatingProvisionParenthetical
3473 Implied Table Table

*

*

 implied:Table
3474 Disclosure of other provisions [abstract] Abstract ifrs-full:DisclosureOfOtherProvisionsAbstract
3475 Cumulative average value Concept (Monetary) For Period Credit ck0001649373:CumulativeAverageValue
3476 Future average value Concept (Monetary) For Period Credit ck0001649373:FutureAverageValue
3477 1269 - Disclosure - Retirement Benefit Plans - Summary of Retirement Benefit Plans (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfRetirementBenefitPlans
3478 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3479 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
3480 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
3481 Surplus [member] Member ck0001649373:SurplusMember
3482 Deficit [member] Member ck0001649373:DeficitsMember
3483 Legal entity [axis] Axis dei:LegalEntityAxis
3484 Entity [Domain] Member dei:EntityDomain
3485 Santander UK Group [member] Member ck0001649373:SantanderUKGroupMember
3486 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3487 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3488 Funded Defined Benefit Pension Scheme [member] Member ifrs-full:WhollyOrPartlyFundedDefinedBenefitPlansMember
3489 Unfunded Defined Benefit Pension Scheme [member] Member ifrs-full:WhollyUnfundedDefinedBenefitPlansMember
3490 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3491 Assets/(liabilities) Abstract ifrs-full:NetAssetsLiabilitiesAbstract
3492 Surplus (deficit) in plan Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
3493 Total net assets Concept (Monetary) As Of Debit ifrs-full:PlanAssetsAtFairValue
3494 1270 - Disclosure - Retirement Benefit Plans - Summary of Remeasurement (Gains)/Losses Recognised In Other Comprehensive Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfRemeasurementGainsLossesRecognisedInOtherComprehensiveIncome
3495 Implied Table Table

*

*

 implied:Table
3496 Disclosure of net defined benefit liability (asset) [abstract] Abstract ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetAbstract
3497 Pension remeasurement Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
3498 1271 - Disclosure - Retirement Benefit Plans - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansAdditionalInformation
3499 Disclosure of defined benefit plans [table] Table

*

*

 ifrs-full:DisclosureOfDefinedBenefitPlansTable
3500 Service concession arrangements [axis] Axis ifrs-full:ServiceConcessionArrangementsAxis
3501 Service concession arrangements [member] Member ifrs-full:ServiceConcessionArrangementsMember
3502 Deficit Repair Contributions [member] Member ck0001649373:DeficitRepairContributionsPlanMember
3503 Deficit Repair Group Section Contributions [member] Member ck0001649373:DeficitRepairGroupSectionContributionsPlanMember
3504 Deficit Group Section Contributions Plan [member] Member ck0001649373:DeficitGroupSectionContributionsPlanMember
3505 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3506 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3507 Santander UK Plc [member] Member ck0001649373:SantanderUkPlcMember
3508 Santander UK Group [member] Member ck0001649373:SantanderUKGroupMember
3509 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3510 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3511 Present value of defined benefit obligations [member] Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
3512 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3513 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3514 Equity collar [member] Member ck0001649373:EquityCollarMember
3515 Legal entity [axis] Axis dei:LegalEntityAxis
3516 Entity [Domain] Member dei:EntityDomain
3517 Santander CF Trustee Limited [member] Member ck0001649373:SantanderCFTrusteeLimitedMember
3518 Santander (UK) Group Pension Scheme Trustees Limited [member] Member ck0001649373:SantanderUkGroupPensionSchemeTrusteesLimitedMember
3519 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
3520 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
3521 Actuarial Assumption of Discount Rates [member] Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
3522 Actuarial Assumption of Expected Rates of Inflation [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfInflationMember
3523 Actuarial assumption of expected rate of pension increases [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfPensionIncreasesMember
3524 Actuarial assumption of mortality rates [member] Member ifrs-full:ActuarialAssumptionOfMortalityRatesMember
3525 Disclosure of defined benefit plans [line items] LineItems ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
3526 Defined contribution expense Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
3527 Key management personnel expense Concept (Text/String) For Period ifrs-full:ExplanationOfValueAssignedToKeyAssumption
3528 Percentage of employee covered defined benefit pension schemes Concept (Percent) As Of ifrs-full:LevelOfParticipationOfEntityComparedWithOtherParticipatingEntities
3529 Number of directors selected Concept (Integer) For Period ck0001649373:NumberOfBoardOfDirectorsInSubsidiary
3530 Number of directors nominated Concept (Integer) For Period ck0001649373:NumberOfNominatedDirectorsInSubsidiary
3531 Number of trustee directors Concept (Integer) For Period ck0001649373:NumberOfTrusteeDirectorsAppointed
3532 Actuarial valuation deficit Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleDecreaseInActuarialAssumption
3533 Estimated increase in liabilities in relation to judgment on GMP equalisation Concept (Monetary) For Period Debit ifrs-full:GainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
3534 Gross notional value Concept (Monetary) As Of Credit ck0001649373:GrossNotionalValuePensionScheme
3535 Equity securities hold Concept (Monetary) As Of Debit ifrs-full:DescriptionOfAmountsOfEntitysOwnFinancialInstrumentsIncludedInFairValueOfPlanAssets
3536 Property occupied Concept (Monetary) As Of Debit ifrs-full:DescriptionOfAmountsOfPropertyOccupiedByEntityIncludedInFairValueOfPlanAssets
3537 Other assets occupied Concept (Monetary) As Of Debit ifrs-full:DescriptionOfAmountsOfOtherAssetsUsedByEntityIncludedInFairValueOfPlanAssets
3538 Contribution to scheme based on agreement Concept (Monetary) As Of Credit ck0001649373:FundingToNewRecoveryPlanBasedOnNewAgreement
3539 Contributions to defined benefit plans Concept (Monetary) For Period Debit ck0001649373:ContributionsToDefinedBenefitPlans
3540 Annual increase in contibution Concept (Percent) For Period ck0001649373:PercentageOfAnnualIncreaseInContributionsToPensionScheme
3541 Maturity date for contribution Concept (Text/String) For Period ifrs-full:DescriptionOfFundingArrangementsAndFundingPolicyThatAffectFutureContributions
3542 Surplus (deficit) in plan Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
3543 Improvements to life expectancy of female employees Concept (Percent) For Period ck0001649373:LifeExpectancyImprovementRateOfFemaleEmployees
3544 Improvements to life expectancy of male employees Concept (Percent) For Period ck0001649373:LifeExpectancyImprovementRateOfMaleEmployees
3545 Average duration of defined benefit obligation Concept (Text/String) For Period ck0001649373:DefinedBenefitObligationWeightedAverageDuration
3546 1272 - Disclosure - Retirement Benefit Plans - Total Defined Benefit Plan Amount Charged to Income Statement (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansTotalDefinedBenefitPlanAmountChargedToIncomeStatement
3547 Implied Table Table

*

*

 implied:Table
3548 Disclosure of net defined benefit liability (asset) [abstract] Abstract ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetAbstract
3549 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
3550 Current service cost Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
3551 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
3552 Administration costs Concept (Monetary) For Period Credit ck0001649373:AdministrationCostsNetDefinedBenefitLiabilityAsset
3553 Total Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInNetDefinedBenefitLiabilityAsset
3554 1273 - Disclosure - Retirement Benefit Plans - Summary of Amounts Recognised in Other Comprehensive Income (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfAmountsRecognisedInOtherComprehensiveIncome
3555 Implied Table Table

*

*

 implied:Table
3556 Disclosure of net defined benefit liability (asset) [abstract] Abstract ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetAbstract
3557 Return on plan assets (excluding amounts included in net interest expense) Concept (Monetary) For Period Debit ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
3558 Actuarial (gains)/losses arising from changes in demographic assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
3559 Actuarial gains arising from experience adjustments Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
3560 Actuarial (gains)/losses arising from changes in financial assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
3561 Pension remeasurement Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
3562 1274 - Disclosure - Retirement Benefit Plans - Disclosure of Movements in Present Value of Defined Benefit Obligations (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansDisclosureOfMovementsInPresentValueOfDefinedBenefitObligations
3563 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3564 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3565 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3566 Present value of defined benefit obligations [member] Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
3567 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3568 Beginning balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3569 Current service cost Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
3570 Current service cost paid by other subsidiaries Concept (Monetary) For Period Credit ck0001649373:CurrentServiceCostPaidByOtherSubsidiaries
3571 Current service cost paid by fellow Banco Santander subsidiaries Concept (Monetary) For Period Credit ck0001649373:CurrentServiceCostPaidByFellowBancoSantanderSubsidiaries
3572 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
3573 Employer salary sacrifice contributions Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
3574 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
3575 GMP equalisation cost Concept (Monetary) For Period Debit ifrs-full:GainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
3576 Remeasurement due to actuarial movements arising from: Abstract ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAssetAbstract
3577 - Changes in demographic assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
3578 - Experience adjustments Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
3579 - Changes in financial assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
3580 Benefits paid Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
3581 Ending balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3582 1275 - Disclosure - Retirement Benefit Plans - Disclosure of Movements in Fair Value of Scheme Assets (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansDisclosureOfMovementsInFairValueOfSchemeAssets
3583 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3584 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3585 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3586 Fair value of scheme assets [member] Member ifrs-full:PlanAssetsMember
3587 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3588 Beginning balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3589 Interest income Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
3590 Contributions paid by employer and scheme members Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
3591 Contributions paid by fellow Banco Santander subsidiaries Concept (Monetary) For Period Debit ck0001649373:ContributionsPaidByFellowBancoSantanderSubsidiaries
3592 Administration costs paid Concept (Monetary) For Period Credit ck0001649373:PaymentOfAdministrationCostsNetDefinedBenefitLiabilityAsset
3593 Return on plan assets (excluding amounts included in net interest expense) Concept (Monetary) For Period Debit ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
3594 Benefits paid Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
3595 Ending balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3596 1276 - Disclosure - Retirement Benefit Plans - Summary of Composition and Fair Value of Plan Assets (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfCompositionAndFairValueOfPlanAssets
3597 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3598 Availiability Of Prices [axis] Axis ck0001649373:AvailiabilityOfPricesAxis
3599 Availiability Of Prices [domain] Member ck0001649373:AvailiabilityOfPricesDomain
3600 Quoted Prices in Active Markets [member] Member ck0001649373:QuotedPricesInActiveMarketsMember
3601 Prices Not Quoted in Active Markets [member] Member ck0001649373:PricesNotQuotedInActiveMarketsMember
3602 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3603 UK equities Concept (Percent) As Of ck0001649373:DomesticEquitiesPercentageContributedToFairValueOfPlanAssets
3604 Overseas equities Concept (Percent) As Of ck0001649373:OverseasEquitiesPercentageContributedToFairValueOfPlanAssets
3605 Corporate bonds Concept (Percent) As Of ck0001649373:CorporateBondsPercentageContributedToFairValueOfPlanAssets
3606 Government fixed interest bonds Concept (Percent) As Of ck0001649373:GovernmentFixedInterestBondsPercentageContributedToFairValueOfPlanAssets
3607 Government index-linked bonds Concept (Percent) As Of ck0001649373:GovernmentIndexlinkedBondsPercentageContributedToFairValueOfPlanAssets
3608 Property Concept (Percent) As Of ck0001649373:PropertyPercentageContributedToFairValueOfPlanAssets
3609 Derivatives Concept (Percent) As Of ck0001649373:DerivativesPercentageContributedToFairValueOfPlanAssets
3610 Cash Concept (Percent) As Of ck0001649373:CashAndCashEquivalentsPercentageContributedToFairValueOfPlanAssets
3611 Repurchase agreements Concept (Percent) As Of ck0001649373:RepurchaseAgreementsPercentageContributedToFairValueOfPlanAssets
3612 Other Concept (Percent) As Of ck0001649373:OtherAssetsPercentageContributedToFairValueOfPlanAssets
3613 Total Concept (Percent) As Of ck0001649373:PercentagesContributedToFairValueOfPlanAssets
3614 UK equities Concept (Monetary) As Of Debit ck0001649373:UkEquitiesAmountContributedToFairValueOfPlanAssets
3615 Overseas equities Concept (Monetary) As Of Debit ck0001649373:OverseasEquitiesAmountContributedToFairValueOfPlanAssets
3616 Corporate bonds Concept (Monetary) As Of Debit ck0001649373:CorporateBondsAmountContributedToFairValueOfPlanAssets
3617 Government fixed interest bonds Concept (Monetary) As Of Debit ck0001649373:GovernmentFixedInterestBondsAmountContributedToFairValueOfPlanAssets
3618 Government index-linked bonds Concept (Monetary) As Of Debit ck0001649373:GovernmentIndexlinkedBondsAmountContributedToFairValueOfPlanAssets
3619 Property Concept (Monetary) As Of Debit ifrs-full:PropertyAmountContributedToFairValueOfPlanAssets
3620 Derivatives Concept (Monetary) As Of Debit ifrs-full:DerivativesAmountContributedToFairValueOfPlanAssets
3621 Cash Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsAmountContributedToFairValueOfPlanAssets
3622 Repurchase agreements Concept (Monetary) As Of Credit ck0001649373:RepurchaseAgreementsAmountContributedToFairValueOfPlanAssets
3623 Other Concept (Monetary) As Of Debit ifrs-full:OtherAssetsAmountContributedToFairValueOfPlanAssets
3624 Total Concept (Monetary) As Of Debit ck0001649373:AggregateAmountContributedToFairValueOfPlanAssets
3625 1277 - Disclosure - Retirement Benefit Plans - Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfPrincipalActuarialAssumptionsUsedForDefinedBenefitSchemes
3626 Implied Table Table

*

*

 implied:Table
3627 Disclosure of sensitivity analysis for actuarial assumptions [abstract] Abstract ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsAbstract
3628 - Discount rate for scheme liabilities Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfDiscountRates
3629 - General price inflation Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfInflation
3630 - General salary increase Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreases
3631 - Expected rate of pension increase Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfPensionIncreases
3632 Longevity at 60 for current pensioners, on the valuation date: Abstract ck0001649373:LongevityAtSixtyForCurrentPensionersOnValuationDateAbstract
3633 - Males Concept (xbrli:durationItemType) For Period ck0001649373:LongevityForCurrentPensionersMalesOne
3634 - Females Concept (xbrli:durationItemType) For Period ck0001649373:LongevityForCurrentPensionersFemalesOne
3635 Longevity at 60 for future pensioners currently aged 40, on the valuation date: Abstract ck0001649373:LongevityAtSixtyForFuturePensionersCurrentlyAgedFortyOnValuationDateAbstract
3636 - Males Concept (xbrli:durationItemType) For Period ck0001649373:LongevityForFuturePensionersMalesOne
3637 - Females Concept (xbrli:durationItemType) For Period ck0001649373:LongevityForFuturePensionersFemalesOne
3638 1278 - Disclosure - Retirement Benefit Plans - Summary of Actuarial Assumption Sensitivities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfActuarialAssumptionSensitivities
3639 Disclosure of sensitivity analysis for actuarial assumptions [table] Table

*

*

 ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsTable
3640 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
3641 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
3642 Actuarial Assumption of Discount Rates [member] Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
3643 Actuarial Assumption of Expected Rates of Inflation [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfInflationMember
3644 Actuarial assumption of expected rates of salary increases [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreasesMember
3645 Actuarial Assumption of Expected Rates of Mortality [member] Member ck0001649373:ActuarialAssumptionOfExpectedRatesOfMortalityMember
3646 Disclosure of sensitivity analysis for actuarial assumptions [line items] LineItems ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
3647 Increase decrease in defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleIncreaseInActuarialAssumption
3648 Description of changes in methods and assumptions Concept (Text/String) For Period ifrs-full:DescriptionOfChangesInMethodsAndAssumptionsUsedInPreparingSensitivityAnalysisForActuarialAssumptions
3649 1279 - Disclosure - Retirement Benefit Plans - Disclosure of Benefits Expected To Be Paid (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRetirementBenefitPlansDisclosureOfBenefitsExpectedToBePaid
3650 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3651 Maturity [axis] Axis ifrs-full:MaturityAxis
3652 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3653 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3654 Later Than 1 Year and Not Later Than 2 Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
3655 2 - 3 years [member] Member ifrs-full:LaterThanTwoYearsAndNotLaterThanThreeYearsMember
3656 3 - 4 years [member] Member ifrs-full:LaterThanThreeYearsAndNotLaterThanFourYearsMember
3657 4 - 5 years [member] Member ifrs-full:LaterThanFourYearsAndNotLaterThanFiveYearsMember
3658 Five Years Ending 2028 [member] Member ifrs-full:LaterThanFiveYearsAndNotLaterThanTenYearsMember
3659 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3660 Benefits expected to be paid Concept (Monetary) As Of Credit ck0001649373:DefinedBenefitPlanExpectedFutureBenefitPayments
3661 1280 - Disclosure - Contingent Liabilities and Commitments - Summary of Contingent Liabilities and Commitments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureContingentLiabilitiesAndCommitmentsSummaryOfContingentLiabilitiesAndCommitments
3662 Disclosure of contingent liabilities [table] Table

*

*

 ifrs-full:DisclosureOfContingentLiabilitiesTable
3663 Classes of contingent liabilities [axis] Axis ifrs-full:ClassesOfContingentLiabilitiesAxis
3664 Contingent liabilities [member] Member ifrs-full:ContingentLiabilitiesMember
3665 Contingent Liability for Guarantees [Member] Member ifrs-full:ContingentLiabilityForGuaranteesMember
3666 Loan commitments [member] Member ifrs-full:LoanCommitmentsMember
3667 Maturity [axis] Axis ifrs-full:MaturityAxis
3668 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3669 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3670 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
3671 Disclosure of contingent liabilities and commitments [line items] LineItems ck0001649373:DisclosureOfContingentLiabilitiesAndCommitmentsLineItems
3672 Guarantees given to third parties Concept (Monetary) As Of Credit ck0001649373:GuaranteesGivenToThirdParties
3673 Formal standby facilities, credit lines and other commitments Concept (Monetary) As Of Credit ck0001649373:StandbyFacilitiesCreditLinesAndOtherCommitments
3674 Guarantees and formal standby facilities, credit lines and other commitments Concept (Monetary) As Of Credit ck0001649373:EstimatedFinancialEffectOfContingentLiabilitiesAndCommitments
3675 1281 - Disclosure - Contingent Liabilities and Commitments - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureContingentLiabilitiesAndCommitmentsAdditionalInformation
3676 Disclosure of contingent liabilities [table] Table

*

*

 ifrs-full:DisclosureOfContingentLiabilitiesTable
3677 Legal entity [axis] Axis dei:LegalEntityAxis
3678 Entity [Domain] Member dei:EntityDomain
3679 Visa Europe Ltd [member] Member ck0001649373:VisaEuropeLtdMember
3680 Range [axis] Axis ifrs-full:RangeAxis
3681 Ranges [member] Member ifrs-full:RangesMember
3682 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3683 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3684 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3685 Compliance with Consumer Credit Act [member] Member ck0001649373:ComplianceWithConsumerCreditActMember
3686 Disclosure of contingent liabilities and commitments [line items] LineItems ck0001649373:DisclosureOfContingentLiabilitiesAndCommitmentsLineItems
3687 Additional operational risk losses and restructuring charges Concept (Monetary) For Period Credit ck0001649373:AdditionalProvisionsOtherProvisionsOperationalRiskLossesAndRestructuringCharges
3688 Sale of share capital Concept (Percent) For Period ck0001649373:VisaEuropeLtdSaleToVisaInc
3689 Losses on litigation settlements Concept (Monetary) For Period Debit ifrs-full:LossesOnLitigationSettlements
3690 Amount of preferred stock upon indemnity more than one billion Concept (Monetary) For Period Debit ck0001649373:AmountOfPreferredStockUponIndemnityMoreThanOneBillion
3691 Description of material leasing arrangements by lessee classified as operating lease Concept (Text/String) For Period ifrs-full:DescriptionOfMaterialLeasingArrangementsByLesseeClassifiedAsOperatingLease
3692 Minimum lease extension period Concept (xbrli:durationItemType) For Period ck0001649373:MinimumLeaseExtensionPeriod
3693 Terms of notice period Concept (xbrli:durationItemType) For Period ck0001649373:TermsOfNoticePeriod
3694 Rental expense Concept (Monetary) For Period Debit ifrs-full:RentalExpense
3695 Minimum rentals Concept (Monetary) For Period Debit ifrs-full:MinimumOperatingLeasePayments
3696 Sub-lease rental income Concept (Monetary) For Period Debit ifrs-full:SubleasePaymentsRecognisedAsExpense
3697 Contingent rent expense Concept (Monetary) For Period Debit ifrs-full:ContingentRentsRecognisedAsExpenseClassifiedAsOperatingLease
3698 1282 - Disclosure - Contingent Liabilities and Commitments - Operating Lease Commitments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureContingentLiabilitiesAndCommitmentsOperatingLeaseCommitments
3699 Disclosure of finance lease and operating lease by lessee [table] Table

*

*

 ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeTable
3700 Maturity [axis] Axis ifrs-full:MaturityAxis
3701 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3702 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3703 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
3704 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
3705 Disclosure of finance lease and operating lease by lessee [line items] LineItems ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeLineItems
3706 Lease payments Concept (Monetary) As Of Credit ifrs-full:MinimumLeasePaymentsPayableUnderNoncancellableOperatingLease
3707 1283 - Disclosure - Share Capital - Schedule of Share Capital Issued and Fully Paid (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureShareCapitalScheduleOfShareCapitalIssuedAndFullyPaid
3708 Implied Table Table

*

*

 implied:Table
3709 Disclosure of classes of share capital [abstract] Abstract ifrs-full:DisclosureOfClassesOfShareCapitalAbstract
3710 Number of shares issued and fully paid Concept (Shares) As Of ifrs-full:NumberOfSharesIssuedAndFullyPaid
3711 Ordinary shares, price per share Concept (Share) As Of ifrs-full:ParValuePerShare
3712 Issued and fully paid share capital Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
3713 1284 - Disclosure - Other Equity Instruments - Summary of Other Equity Instruments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherEquityInstrumentsSummaryOfOtherEquityInstruments
3714 Disclosure of other equity instruments [table] Table

*

*

 ck0001649373:DisclosureOfOtherEquityInstrumentsTable
3715 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3716 Equity [member] Member ifrs-full:EquityMember
3717 500m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:FiveHundredMillionFixedRateResetPerpetualATOneCapitalSecuritiesMember
3718 750m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:SevenHundredAndFiftyMillionFixedRatePerpetualATOneCapitalSecuritiesMember
3719 300m Perpetual Capital Securities [member] Member ck0001649373:ThreeHundredMillionPerpetualCapitalSecuritiesMember
3720 500m Perpetual Capital Securities [member] Member ck0001649373:FiveHundredMillionPerpetualCapitalSecuritiesMember
3721 Disclosure of other equity instruments [line items] LineItems ck0001649373:DisclosureOfOtherEquityInstrumentsLineItems
3722 Initial interest rate Concept (Percent) For Period ck0001649373:PercentageOnOtherEquityInterest
3723 First call date Concept (Year/Month) For Period ck0001649373:OtherEquityInterestMaturityPeriod
3724 Other equity instruments Concept (Monetary) As Of Credit ifrs-full:OtherEquityInterest
3725 1285 - Disclosure - Other Equity Instruments - Summary of Other Equity Instruments (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherEquityInstrumentsSummaryOfOtherEquityInstrumentsParenthetical
3726 Disclosure of other equity instruments [table] Table

*

*

 ck0001649373:DisclosureOfOtherEquityInstrumentsTable
3727 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3728 Equity [member] Member ifrs-full:EquityMember
3729 500m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:FiveHundredMillionFixedRateResetPerpetualATOneCapitalSecuritiesMember
3730 750m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:SevenHundredAndFiftyMillionFixedRatePerpetualATOneCapitalSecuritiesMember
3731 300m Perpetual Capital Securities [member] Member ck0001649373:ThreeHundredMillionPerpetualCapitalSecuritiesMember
3732 500m Perpetual Capital Securities [member] Member ck0001649373:FiveHundredMillionPerpetualCapitalSecuritiesMember
3733 Disclosure of other equity instruments [line items] LineItems ck0001649373:DisclosureOfOtherEquityInstrumentsLineItems
3734 Capital securities Concept (Monetary) For Period Credit ck0001649373:CapitalSecuritiesIssued
3735 1286 - Disclosure - Other Equity Instruments - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherEquityInstrumentsAdditionalInformation
3736 Disclosure of other equity instruments [table] Table

*

*

 ck0001649373:DisclosureOfOtherEquityInstrumentsTable
3737 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3738 Equity [member] Member ifrs-full:EquityMember
3739 500m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:FiveHundredMillionFixedRateResetPerpetualATOneCapitalSecuritiesMember
3740 300m Perpetual Capital Securities [member] Member ck0001649373:ThreeHundredMillionPerpetualCapitalSecuritiesMember
3741 500m Perpetual Capital Securities [member] Member ck0001649373:FiveHundredMillionPerpetualCapitalSecuritiesMember
3742 Hundred Million Of The Seven Hundred And Fifty Million Fixed Rate Reset Perpetual At One Capital Securities [member] Member ck0001649373:HundredMillionOfTheSevenHundredAndFiftyMillionFixedRateResetPerpetualAtOneCapitalSecuritiesMember
3743 750m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:SevenHundredAndFiftyMillionFixedRatePerpetualATOneCapitalSecuritiesMember
3744 Disclosure of other equity instruments [line items] LineItems ck0001649373:DisclosureOfOtherEquityInstrumentsLineItems
3745 Common equity tier 1 capital ratio minimum Concept (Percent) For Period ck0001649373:CommonEquityTierOneCapitalRatioMinimum
3746 Distribution rate resets, period Concept (xbrli:durationItemType) For Period ck0001649373:DistributionRateResetsBasedOnPrevailingFiveYearSterlingMidSwapRatePeriod
3747 Perpetual Capital Securities issued Concept (Monetary) For Period Credit ck0001649373:CapitalSecuritiesIssued
3748 1287 - Disclosure - Non-Controlling Interests - Schedule of Amounts Attributable to Non-Controlling Interests (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNonControllingInterestsScheduleOfAmountsAttributableToNonControllingInterests
3749 Disclosure of Non-controlling Interests [table] Table

*

*

 ck0001649373:DisclosureOfNoncontrollingInterestsTable
3750 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3751 Equity [member] Member ifrs-full:EquityMember
3752 300m Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001649373:ThreeHundredMillionFixedOrFloatingRateNoncumulativeCallablePreferenceSharesMember
3753 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001649373:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3754 PSA Finance UK Limited [member] Member ck0001649373:PSAFinanceUKLimitedMember
3755 Disclosure of noncontrolling interests [line items] LineItems ck0001649373:DisclosureOfNoncontrollingInterestsLineItems
3756 Fixed non-cumulative annual dividend payable percentage Concept (Percent) For Period ck0001649373:FixedNoncumulativeAnnualDividendPayablePercentage
3757 Reserve Capital Instruments annual bear interest rate Concept (Percent) For Period ck0001649373:StepUpCallablePerpetualReserveCapitalInstrumentsAnnualBearInterestRate
3758 First call date Concept (Year/Month) For Period ck0001649373:NoncontrollingInterestMaturityPeriod
3759 Non-controlling interests Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
3760 1288 - Disclosure - Non-Controlling Interests - Schedule of Amounts Attributable to Non-Controlling Interests (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNonControllingInterestsScheduleOfAmountsAttributableToNonControllingInterestsParenthetical
3761 Disclosure of Non-controlling Interests [table] Table

*

*

 ck0001649373:DisclosureOfNoncontrollingInterestsTable
3762 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3763 Equity [member] Member ifrs-full:EquityMember
3764 300m Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001649373:ThreeHundredMillionFixedOrFloatingRateNoncumulativeCallablePreferenceSharesMember
3765 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001649373:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3766 Disclosure of noncontrolling interests [line items] LineItems ck0001649373:DisclosureOfNoncontrollingInterestsLineItems
3767 Notional amount Concept (Monetary) As Of ifrs-full:NotionalAmount
3768 1289 - Disclosure - Non-Controlling Interests - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureNonControllingInterestsAdditionalInformation
3769 Disclosure of Non-controlling Interests [table] Table

*

*

 ck0001649373:DisclosureOfNoncontrollingInterestsTable
3770 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3771 Equity [member] Member ifrs-full:EquityMember
3772 300m Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001649373:ThreeHundredMillionFixedOrFloatingRateNoncumulativeCallablePreferenceSharesMember
3773 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001649373:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3774 Disclosure of noncontrolling interests [line items] LineItems ck0001649373:DisclosureOfNoncontrollingInterestsLineItems
3775 Fixed non-cumulative annual dividend payable percentage Concept (Percent) For Period ck0001649373:FixedNoncumulativeAnnualDividendPayablePercentage
3776 Fixed non-cumulative quarterly dividend payable percentage Concept (Percent) For Period ck0001649373:FixedNoncumulativeQuarterlyDividendPayablePercentage
3777 Reserve Capital Instruments bear interest rate reset period Concept (xbrli:durationItemType) For Period ck0001649373:StepUpCallablePerpetualReserveCapitalInstrumentsBearInterestRateResetPeriod
3778 Reserve Capital Instruments benchmark gilt rate period Concept (xbrli:durationItemType) For Period ck0001649373:StepUpCallablePerpetualReserveCapitalInstrumentsBearInterestRateGiltRateBenchmarkPeriod
3779 1290 - Disclosure - Changes in Liabilities Arising From Financing Activities - Summary of Changes in Liabilities Arising from Financing Activities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureChangesInLiabilitiesArisingFromFinancingActivitiesSummaryOfChangesInLiabilitiesArisingFromFinancingActivities
3780 Disclosure of reconciliation of liabilities arising from financing activities [table] Table

*

*

 ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesTable
3781 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3782 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3783 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
3784 Subordinated liabilities [member] Member ck0001649373:SubordinatedLiabilitiesMember
3785 Other Equity Instruments [member] Member ifrs-full:OtherEquityInterestMember
3786 Dividends Paid [member] Member ck0001649373:DividendsPaidMember
3787 Disclosure of reconciliation of liabilities arising from financing activities [line items] LineItems ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesLineItems
3788 Beginning Balance Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
3789 Cash flows from financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
3790 Cash flows from operating activities Concept (Monetary) For Period ck0001649373:CashFlowsFromUsedInOperatingActivitiesArisingFromChangeInLiabilitiesOfFinancing
3791 - Unrealised foreign exchange Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughEffectOfChangesInForeignExchangeRatesLiabilitiesArisingFromFinancingActivities
3792 - Other changes Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughOtherChangesLiabilitiesArisingFromFinancingActivities
3793 Ending Balance Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
3794 1291 - Disclosure - Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Financial Assets Charged as Security Under On-Balance Sheet and Off-Balance (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAssetsChargedAsSecurityForLiabilitiesAndCollateralAcceptedAsSecurityForAssetsFinancialAssetsChargedAsSecurityUnderOnBalanceSheetAndOffBalance
3795 Disclosure of assets pledged as security [table] Table

*

*

 ck0001649373:DisclosureOfAssetsPledgedAsSecurityTable
3796 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
3797 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
3798 On-Balance Sheet [member] Member ck0001649373:OnBalanceSheetMember
3799 Off-Balance Sheet [member] Member ck0001649373:OffBalanceSheetMember
3800 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3801 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3802 Cash and Balances at Central Banks [member] Member ck0001649373:CashAndBalancesWithCentralBanksMember
3803 Trading Assets [member] Member ck0001649373:TradingAssetsMember
3804 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
3805 Loans and advances to banks [member] Member ck0001649373:LoansAndAdvancesToBanksMember
3806 Other financial assets at amortised cost [member] Member ck0001649373:OtherFinancialAssetsAtAmortisedCostMember
3807 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
3808 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
3809 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3810 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3811 Securitisations and Covered Bonds [member] Member ck0001649373:SecuritisationsAndCoveredBondsMember
3812 Other [member] Member ck0001649373:OtherMember
3813 Disclosure of assets pledged as security [line items] LineItems ck0001649373:DisclosureOfAssetsPledgedAsSecurityLineItems
3814 Assets charged as security for liabilities Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
3815 1292 - Disclosure - Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAssetsChargedAsSecurityForLiabilitiesAndCollateralAcceptedAsSecurityForAssetsAdditionalInformation
3816 Disclosure of assets pledged as security [table] Table

*

*

 ck0001649373:DisclosureOfAssetsPledgedAsSecurityTable
3817 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3818 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3819 Fellow Subsidiaries [member] Member ifrs-full:SubsidiariesMember
3820 Santander UK Plc [member] Member ck0001649373:SantanderUkPlcMember
3821 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3822 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3823 Sale and Repurchase Agreements [member] Member ck0001649373:SaleAndRepurchaseAgreementsMember
3824 Loans and advances to customers- securitisations and covered bonds [member] Member ck0001649373:LoansAndAdvancesToCustomersSecuritisationsAndCoveredBondsMember
3825 Internally Retained [member] Member ck0001649373:InternallyRetainedMember
3826 Third Party Bilateral Secured Funding Transactions [member] Member ck0001649373:ThirdPartyBilateralSecuredFundingTransactionsMember
3827 Cash [member] Member ck0001649373:Cash1Member
3828 Purchase and resale agreements [member] Member ck0001649373:PurchaseAndResaleAgreementsMember
3829 Continuing involvement in derecognised financial assets by type of transfer [axis] Axis ifrs-full:ContinuingInvolvementInDerecognisedFinancialAssetsByTypeOfTransferAxis
3830 Types of transfer [member] Member ifrs-full:TypesOfTransferMember
3831 Securitisations and Covered Bonds [member] Member ck0001649373:SecuritisationsAndCoveredBondsMember
3832 Securities Lending [member] Member ifrs-full:SecuritiesLendingMember
3833 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3834 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3835 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
3836 Disclosure of assets pledged as security [line items] LineItems ck0001649373:DisclosureOfAssetsPledgedAsSecurityLineItems
3837 Assets charged as security for liabilities Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
3838 Gross assets charged as security for liabilities Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedInEntitysFinancialStatementsInRelationToStructuredEntities
3839 Internally retained securitisation and covered bond issuances available for creating collateral Concept (Monetary) As Of Debit ck0001649373:NoteIssuancesAvailableForCreatingCollateral
3840 Notes issued under securitisation and covered bond programmes retained internally Concept (Monetary) As Of Credit ifrs-full:NotesAndDebenturesIssued
3841 Assets charged as security for liabilities Concept (Monetary) As Of Debit ck0001649373:AssetsPledgedAsCollateralForLiabilities
3842 Collateral accepted as security for assets Concept (Monetary) As Of Credit ck0001649373:CollateralAcceptedAsSecurityForAssets
3843 1293 - Disclosure - Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Schedule of Collateral Held as Security for Assets (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureAssetsChargedAsSecurityForLiabilitiesAndCollateralAcceptedAsSecurityForAssetsScheduleOfCollateralHeldAsSecurityForAssets
3844 Disclosure of assets pledged as security [table] Table

*

*

 ck0001649373:DisclosureOfAssetsPledgedAsSecurityTable
3845 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
3846 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
3847 On-Balance Sheet [member] Member ck0001649373:OnBalanceSheetMember
3848 Off-Balance Sheet [member] Member ck0001649373:OffBalanceSheetMember
3849 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3850 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3851 Trading Liabilities [member] Member ck0001649373:TradingLiabilities1Member
3852 Deposits by customers [member] Member ck0001649373:DepositsByCustomersMember
3853 Deposits by banks [member] Member ck0001649373:DepositsByBanksMember
3854 Disclosure of assets pledged as security [line items] LineItems ck0001649373:DisclosureOfAssetsPledgedAsSecurityLineItems
3855 Total on-balance sheet/ off-balance sheet Concept (Monetary) As Of Credit ck0001649373:CollateralAcceptedAsSecurityForAssets
3856 1294 - Disclosure - Share-Based Compensation - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureShareBasedCompensationAdditionalInformation
3857 Disclosure of terms and conditions of share-based payment arrangement [table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
3858 Range [axis] Axis ifrs-full:RangeAxis
3859 Ranges [member] Member ifrs-full:RangesMember
3860 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3861 Top of Range [member] Member ifrs-full:TopOfRangeMember
3862 Variable Pay of Less Than 500,000 [member] Member ck0001649373:VariablePayOfLessThan500000Member
3863 Variable Pay at or Above 500,000 [member] Member ck0001649373:VariablePayAtOrAbove500000Member
3864 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3865 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3866 Long-Term Incentive Plan (LTIP) [member] Member ck0001649373:LongtermIncentivePlanMember
3867 Share Incentive Plans [member] Member ck0001649373:ShareIncentivePlansMember
3868 Regulatory deferral account balances [axis] Axis ifrs-full:RegulatoryDeferralAccountBalancesAxis
3869 Regulatory deferral account balances [member] Member ifrs-full:RegulatoryDeferralAccountBalancesMember
3870 Cash [member] Member ck0001649373:Cash1Member
3871 Shares [member] Member ck0001649373:SharesMember
3872 Title of individual 1 [axis] Axis ck0001649373:TitleOfIndividual1Axis
3873 Government Grants [domain] Member ck0001649373:GovernmentGrantsDomain
3874 Employees [member] Member ck0001649373:MaterialRiskTakersMember
3875 Disclosure of terms and conditions of share-based payment arrangement [line items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
3876 Liabilities arising from share-based payment transactions Concept (Monetary) As Of Credit ifrs-full:LiabilitiesFromSharebasedPaymentTransactions2011
3877 Liabilities arising from share-based payment transactions, vested liabilities Concept (Monetary) As Of Credit ifrs-full:IntrinsicValueOfLiabilitiesFromSharebasedPaymentTransactionsForWhichCounterpartysRightToCashOrOtherAssetsVested2011
3878 Number of sharesave schemes launched Concept (Integer) For Period ck0001649373:NumberOfSharesaveScehmesLaunched
3879 Year of grant of share-based payment arrangement Concept (Text/String) For Period ifrs-full:DateOfGrantOfSharebasedPaymentArrangement
3880 Employee saving on share based compensation Concept (Monetary) As Of Debit ck0001649373:EstimatedEmployeeSavingOnShareBasedCompensationPlan
3881 Terms of options Concept (xbrli:durationItemType) For Period ck0001649373:MaximumTermOfOptionsGrantedForShareBasedPaymentsArrangement
3882 Discount percent on share price under share based compensation plan Concept (Percent) For Period ck0001649373:EstimatedDiscountPercentOnSharePriceUnderShareBasedCompensationPlan
3883 Weighted average share price Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsInSharebasedPaymentArrangementExercisedDuringPeriodAtDateOfExercise
3884 Weighted average grant-date fair value Concept (Monetary) As Of Credit ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
3885 LTIP awarded Concept (Decimal) For Period ifrs-full:NumberOfInstrumentsOtherEquityInstrumentsGranted
3886 Percent of other equity instruments vested Concept (Percent) For Period ck0001649373:PercentOfOtherEquityInstrumentsVestedInSharebasedPaymentArrangement
3887 Annual bonus percentage Concept (Percent) For Period ck0001649373:AnnualBonusPercentage
3888 Deferred shares description Concept (Text/String) For Period ck0001649373:DeferredShareAwardsDescription
3889 Percentage of defer annual bonus Concept (Percent) For Period ck0001649373:PercentageOfDeferAnnualBonus
3890 Maximum investment value per tax year Concept (Monetary) As Of Debit ck0001649373:MaximumNetInvestmentValue
3891 Percentage of maximum salary that can be invested Concept (Percent) For Period ck0001649373:PercentageOfMaximumSalaryThatCanBeInvested
3892 Vesting requirements for sharebased payment arrangement Concept (Text/String) For Period ifrs-full:DescriptionOfVestingRequirementsForSharebasedPaymentArrangement
3893 Number of shares outstanding Concept (Shares) For Period ifrs-full:IncreaseDecreaseInNumberOfSharesOutstanding
3894 1295 - Disclosure - Share-Based Compensation - Summary of Movement in Share Options (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureShareBasedCompensationSummaryOfMovementInShareOptions
3895 Disclosure of terms and conditions of share-based payment arrangement [table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
3896 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3897 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3898 Sharesave Schemes [member] Member ck0001649373:SharesaveSchemesMember
3899 Disclosure of terms and conditions of share-based payment arrangement [line items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
3900 Number of options outstanding beginning balance Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
3901 Number of options granted Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
3902 Number of options exercised Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
3903 Number of options forfeited/expired Concept (Decimal) For Period ck0001649373:NumberOfShareOptionsForfeitedOrExpiredInSharebasedPaymentArrangement
3904 Number of options outstanding ending balance Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
3905 Number of options exercisable Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
3906 Weighted average exercise price outstanding beginning balance Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
3907 Weighted average exercise price granted Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsGrantedInSharebasedPaymentArrangement
3908 Weighted average exercise price exercised Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisedInSharebasedPaymentArrangement
3909 Weighted average exercise price forfeited/expired Concept (Monetary) For Period ck0001649373:WeightedAverageExercisePriceOfShareOptionsForfeitedOrExpiredInSharebasedPaymentArrangement
3910 Weighted average exercise price outstanding ending balance Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
3911 Weighted average exercise price exercisable ending balance Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
3912 1296 - Disclosure - Share-Based Compensation - Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureShareBasedCompensationSummaryOfRangeOfExercisePricesAndWeightedAverageRemainingContractualLifeOfTheOptionsOutstanding
3913 Disclosure of number and weighted average remaining contractual life of outstanding share options [table] Table

*

*

 ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsTable
3914 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3915 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3916 Sharesave Schemes [member] Member ck0001649373:SharesaveSchemesMember
3917 Ranges of exercise prices for outstanding share options [axis] Axis ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsAxis
3918 Ranges of exercise prices for outstanding share options [member] Member ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsMember
3919 2 to 3 [member] Member ck0001649373:PoundTwoToPoundThreeMember
3920 3 to 4 [member] Member ck0001649373:PoundThreeToPoundFourMember
3921 4 to 5 [member] Member ck0001649373:PoundFourToPoundFiveMember
3922 Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] LineItems ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsLineItems
3923 Options outstanding , Weighted average remaining contractual life years Concept (xbrli:durationItemType) For Period ck0001649373:WeightedAveragesRemainingContractualLifeOfOutstandingShareOptions
3924 Option outstanding, Weighted average exercise price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
3925 1297 - Disclosure - Share-Based Compensation - Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureShareBasedCompensationSummaryOfRangeOfExercisePricesAndWeightedAverageRemainingContractualLifeOfTheOptionsOutstandingParenthetical
3926 Disclosure of number and weighted average remaining contractual life of outstanding share options [table] Table

*

*

 ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsTable
3927 Ranges of exercise prices for outstanding share options [axis] Axis ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsAxis
3928 Ranges of exercise prices for outstanding share options [member] Member ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsMember
3929 2 to 3 [member] Member ck0001649373:PoundTwoToPoundThreeMember
3930 3 to 4 [member] Member ck0001649373:PoundThreeToPoundFourMember
3931 4 to 5 [member] Member ck0001649373:PoundFourToPoundFiveMember
3932 Range [axis] Axis ifrs-full:RangeAxis
3933 Ranges [member] Member ifrs-full:RangesMember
3934 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3935 Top of Range [member] Member ifrs-full:TopOfRangeMember
3936 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3937 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3938 Sharesave Schemes [member] Member ck0001649373:SharesaveSchemesMember
3939 Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] LineItems ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsLineItems
3940 Range of exercise prices Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
3941 1298 - Disclosure - Share-Based Compensation - Summary of Movement in Value of Conditional Awards in LTIPs (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureShareBasedCompensationSummaryOfMovementInValueOfConditionalAwardsInLTIPs
3942 Disclosure of terms and conditions of share-based payment arrangement [table] Table

*

*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
3943 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3944 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3945 2015 LTIP [member] Member ck0001649373:TwoThousandAndFifteenLongTermIncentivePlanMember
3946 2014 LTIP [member] Member ck0001649373:TwoThousandAndFourteenLongTermIncentivePlanMember
3947 Disclosure of terms and conditions of share-based payment arrangement [line items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
3948 Conditional awards at the beginning of the year Concept (Monetary) As Of Credit ck0001649373:ConditionalAwards
3949 Conditional awards forfeited or cancelled Concept (Monetary) For Period Debit ck0001649373:ConditionalAwardsForfeitedOrCancelled
3950 Conditional awards outstanding at the end of the year Concept (Monetary) As Of Credit ck0001649373:ConditionalAwards
3951 1299 - Disclosure - Transactions With Directors and Other Key Management Personnel - Summary of Remuneration of the Directors and Other Key Management Personnel (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransactionsWithDirectorsAndOtherKeyManagementPersonnelSummaryOfRemunerationOfTheDirectorsAndOtherKeyManagementPersonnel
3952 Implied Table Table

*

*

 implied:Table
3953 Disclosure Of Remuneration Of Directors And Other Key Management Personnel [abstract] Abstract ck0001649373:DisclosureOfRemunerationOfDirectorsAndOtherKeyManagementPersonnelAbstract
3954 Salaries and fees Concept (Monetary) For Period Debit ck0001649373:DirectorsSalariesAndFees
3955 Performance-related payments Concept (Monetary) For Period Debit ck0001649373:DirectorsPerformanceRelatedPayments
3956 Other fixed remuneration (pension and other allowances & non-cash benefits) Concept (Monetary) For Period Debit ck0001649373:DirectorsExpenses
3957 Expenses Concept (Monetary) For Period Debit ifrs-full:DirectorsRemunerationExpense
3958 Total remuneration Concept (Monetary) For Period Debit ck0001649373:DirectorsRemuneration
3959 Short-term employee benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationShorttermEmployeeBenefits
3960 Post-employment benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationPostemploymentBenefits
3961 Total compensation Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensation
3962 1300 - Disclosure - Transactions With Directors and Other Key Management Personnel - Summary of Remuneration of the Directors and Other Key Management Personnel (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransactionsWithDirectorsAndOtherKeyManagementPersonnelSummaryOfRemunerationOfTheDirectorsAndOtherKeyManagementPersonnelParenthetical
3963 Disclosure Of Directors And Key Management Remuneration [table] Table

*

*

 ck0001649373:DisclosureOfDirectorsAndKeyManagementRemunerationTable
3964 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3965 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3966 Banco Santander SA London Branch [member] Member ck0001649373:BancoSantanderSALondonBranchMember
3967 Disclosure of directors and key management remuneration [line items] LineItems ck0001649373:DisclosureOfDirectorsAndKeyManagementRemunerationLineItems
3968 Payments made as buy-outs of deferred performance-related payment Concept (Monetary) For Period Debit ck0001649373:DeferredPerformanceRelatedPayments
3969 Number of shares made as buy-outs of deferred performance-related payment Concept (Shares) For Period ck0001649373:DeferredPerformanceRelatedNumberOfShares
3970 Number of previously employed individuals for buy-out of deferred performance related payment Concept (Integer) For Period ck0001649373:NumberOfPreviouslyEmployedIndividualsForBuyoutsOfDeferredPerformanceRelatedPayments
3971 Termination payment Concept (Monetary) For Period Debit ifrs-full:TerminationBenefitsExpense
3972 Number key management persons who receives termination benefit Concept (Integer) For Period ck0001649373:NumberOfKeyManagementPersonnelWhoReceiveTerminationBenefit
3973 1301 - Disclosure - Transactions With Directors and Other Key Management Personnel - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransactionsWithDirectorsAndOtherKeyManagementPersonnelAdditionalInformation
3974 Disclosure Of Directors And Key Management Remuneration [table] Table

*

*

 ck0001649373:DisclosureOfDirectorsAndKeyManagementRemunerationTable
3975 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3976 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3977 Banco Santander SA [member] Member ck0001649373:BancoSantanderSAMember
3978 Other key management personnel [member] Member ck0001649373:OtherKeyManagementPersonnelMember
3979 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
3980 Remuneration excluding pension contribution Concept (Monetary) For Period Credit ck0001649373:DirectorsRemunerationExpenseHighestPaidDirector
3981 Remuneration excluding pension contribution performance related Concept (Monetary) For Period Debit ck0001649373:RemunerationExcludingPensionContributionPerformanceRelatedHighestPaidDirector
3982 Deferred pension benefit accruing under a defined benefit scheme Concept (Monetary) For Period Debit ck0001649373:DeferredPensionBenefitAccruingUnderDefinedBenefitScheme
3983 Ex gratia pensions paid to former Directors Concept (Monetary) For Period Debit ck0001649373:ExgratiaPensionsPaid
3984 Sharedealing transactions through the Santander UK group's Concept (Monetary) For Period Debit ck0001649373:DirectorsSharedealingTransactionsValue
3985 Number of Directors undertook sharedealing transactions Concept (Integer) For Period ck0001649373:NumberOfDirectorsWhoUndertookSharedealingTransactions
3986 Loans made to directors Concept (Monetary) For Period Credit ck0001649373:DirectorsLoansPrincipalAmountOutstanding
3987 Number of loan made to directors Concept (Integer) For Period ck0001649373:NumberOfLoansMadeToDirectors
3988 Benefits paid in kind for directors Concept (Monetary) For Period Debit ifrs-full:DirectorsRemunerationExpense
3989 Number of directors paid in kind Concept (Integer) For Period ck0001649373:NumberOfDirectors
3990 Benefits paid in kind for key management Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensation
3991 Number of key management paid in kind Concept (Integer) For Period ck0001649373:NumberOfKeyManagementPersonnel
3992 Directors who held any interest in the shares Concept (Integer) For Period ck0001649373:NumberOfDirectorsWhoHeldInterestInShares
3993 Directors who exercised or were granted any rights to subscribe for shares Concept (Integer) For Period ck0001649373:NumberOfDirectorsWhoExercisedOrWereGrantedAnyRightsToSubscribeForShares
3994 Loans made to key management personnel Concept (Monetary) For Period Credit ifrs-full:CashAdvancesAndLoansMadeToRelatedParties
3995 Number of loan made to key management personnel Concept (Integer) For Period ck0001649373:NumberOfLoansMadeToKeyManagementPersonnel
3996 1302 - Disclosure - Transactions With Directors and Other Key Management Personnel - Summary of Transactions with Directors, Other Key Management Personnel (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransactionsWithDirectorsAndOtherKeyManagementPersonnelSummaryOfTransactionsWithDirectorsOtherKeyManagementPersonnel
3997 Disclosure Of Directors And Key Management Remuneration [table] Table

*

*

 ck0001649373:DisclosureOfDirectorsAndKeyManagementRemunerationTable
3998 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3999 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4000 Key management personnel of entity or parent [member] Member ifrs-full:KeyManagementPersonnelOfEntityOrParentMember
4001 Disclosure of directors and key management remuneration [line items] LineItems ck0001649373:DisclosureOfDirectorsAndKeyManagementRemunerationLineItems
4002 Number of secured loans, unsecured loans and overdrafts, beginning balance Concept (Integer) As Of ck0001649373:NumberOfSecuredLoansUnsecuredLoansAndOverdrafts
4003 Number of secured loans, unsecured loans and overdrafts, net movements Concept (Integer) For Period ck0001649373:NumberOfSecuredLoansUnsecuredLoansAndOverdraftsNetMovement
4004 Number of secured loans, unsecured loans and overdrafts, ending balance Concept (Integer) As Of ck0001649373:NumberOfSecuredLoansUnsecuredLoansAndOverdrafts
4005 Beginning balance Concept (Monetary) As Of Credit ck0001649373:SecuredLoansUnsecuredLoansAndOverdrafts
4006 Net movements Concept (Monetary) For Period Debit ck0001649373:SecuredLoansUnsecuredLoansAndOverdraftsNetMovements
4007 Ending balance Concept (Monetary) As Of Credit ck0001649373:SecuredLoansUnsecuredLoansAndOverdrafts
4008 Number of deposit, bank and instant access accounts and investments, beginning balance Concept (Integer) As Of ck0001649373:NumberOfDepositBankAndInstantAccessAccountsAndInvestments
4009 Number of deposit, bank and instant access accounts and investments, net movements Concept (Integer) For Period ck0001649373:NumberOfDepositBankAndInstantAccessAccountsAndInvestmentsNetMovement
4010 Number of deposit, bank and instant access accounts and investments, ending balance Concept (Integer) As Of ck0001649373:NumberOfDepositBankAndInstantAccessAccountsAndInvestments
4011 Beginning balance Concept (Monetary) As Of Credit ck0001649373:DepositBankAndInstantAccessAccountsAndInvestments
4012 Net movements Concept (Monetary) For Period Debit ck0001649373:DepositBankAndInstantAccessAccountsAndInvestmentsNetMovement
4013 Ending balance Concept (Monetary) As Of Credit ck0001649373:DepositBankAndInstantAccessAccountsAndInvestments
4014 1303 - Disclosure - Related Party Disclosures - Summary of Transactions With Related Parties (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRelatedPartyDisclosuresSummaryOfTransactionsWithRelatedParties
4015 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
4016 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4017 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4018 Ultimate Parent [Member] Member ck0001649373:UltimateParentMember
4019 Fellow Subsidiaries [member] Member ifrs-full:SubsidiariesMember
4020 Associates and Joint Ventures [Member] Member ck0001649373:AssociatesAndJointVenturesMember
4021 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
4022 Interest, fees and other income received Concept (Monetary) For Period Credit ck0001649373:InterestFeesAndOtherIncomeReceived
4023 Interest, fees and other expenses paid Concept (Monetary) For Period Debit ck0001649373:InterestFeesAndOtherExpensePaid
4024 Amounts owed by related parties Concept (Monetary) As Of Debit ifrs-full:AmountsReceivableRelatedPartyTransactions
4025 Amounts owed to related parties Concept (Monetary) As Of Credit ifrs-full:AmountsPayableRelatedPartyTransactions
4026 1304 - Disclosure - Related Party Disclosures - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRelatedPartyDisclosuresAdditionalInformation
4027 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
4028 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4029 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4030 Banco Santander London Branch [member] Member ck0001649373:BancoSantanderLondonBranchMember
4031 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4032 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4033 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
4034 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
4035 Customer loans Concept (Monetary) As Of Debit ifrs-full:ConsumerLoans
4036 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
4037 Liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
4038 Decrease in RWAs due to transfers Concept (Monetary) For Period Debit ck0001649373:DecreaseInRiskweightedAssetsDueToModelChanges
4039 Dividend paid Concept (Monetary) For Period Debit ifrs-full:DividendsPaid
4040 1305 - Disclosure - Financial Instruments - Analysis of Fair Value of Financial Instruments Carried at Amortised (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsAnalysisOfFairValueOfFinancialInstrumentsCarriedAtAmortised
4041 Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [table] Table

*

*

 ck0001649373:DisclosureOfFairValuesOfFinancialInstrumentsCarriedAtAmortisedCostTable
4042 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4043 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4044 Level 1 [member] Member ifrs-full:Level1OfFairValueHierarchyMember
4045 Level 2 [member] Member ifrs-full:Level2OfFairValueHierarchyMember
4046 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4047 Fair Value [member] Member ifrs-full:AtFairValueMember
4048 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4049 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4050 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4051 Loans and advances to banks [member] Member ck0001649373:LoansAndAdvancesToBanksMember
4052 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
4053 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
4054 Categories of financial liabilities [axis] Axis ifrs-full:CategoriesOfFinancialLiabilitiesAxis
4055 Financial liabilities, category [member] Member ifrs-full:FinancialLiabilitiesCategoryMember
4056 Deposits by customers [member] Member ck0001649373:DepositsByCustomersMember
4057 Deposits by banks [member] Member ck0001649373:DepositsByBanksMember
4058 Repurchase agreements - non trading [member] Member ck0001649373:RepurchaseAgreementsNontradingMember
4059 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
4060 Subordinated liabilities [member] Member ck0001649373:SubordinatedLiabilitiesMember
4061 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
4062 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
4063 Financial Liabilities at Amortised Cost, Category [member] Member ifrs-full:FinancialLiabilitiesAtAmortisedCostCategoryMember
4064 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4065 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4066 Financial assets at amortised cost [member] Member ifrs-full:FinancialAssetsAtAmortisedCostMember
4067 Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [line items] LineItems ck0001649373:DisclosureOfFairValuesOfFinancialInstrumentsCarriedAtAmortisedCostLineItems
4068 Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
4069 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
4070 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
4071 Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
4072 Financial investments Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
4073 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
4074 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
4075 Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
4076 Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
4077 Other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001649373:OtherFinancialAssetsAtAmortisedCost
4078 Financial investments Concept (Monetary) As Of Debit ck0001649373:FinancialInvestments
4079 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
4080 1306 - Disclosure - Financial Instruments - Fair Values of Financial Instruments Measured at Fair Value on a Recurring Basis (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsFairValuesOfFinancialInstrumentsMeasuredAtFairValueOnARecurringBasis
4081 Disclosure of fair value measurement of assets [table] Table

*

*

 ifrs-full:DisclosureOfFairValueMeasurementOfAssetsTable
4082 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4083 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4084 Securities Purchased Under Resale Agreements [member] Member ck0001649373:SecuritiesPurchasedUnderResaleAgreementsMember
4085 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
4086 Equity securities [member] Member ifrs-full:TradingEquitySecuritiesMember
4087 Cash Collateral [member] Member ck0001649373:CashCollateralMember
4088 Short-term loans [member] Member ck0001649373:ShortTermLoansMember
4089 Exchange Rate Contracts [member] Member ck0001649373:ExchangeRateContractsMember
4090 Interest Rate Contracts [member] Member ifrs-full:InterestRateSwapContractMember
4091 Equity and Credit Contracts [member] Member ck0001649373:EquityAndCreditContractsMember
4092 Netting [member] Member ck0001649373:NettingContractsMember
4093 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4094 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
4095 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
4096 Available for sale debt securities [member] Member ck0001649373:AvailableForSaleDebtSecuritiesMember
4097 Available for sale equity securities [member] Member ck0001649373:AvailableForSaleEquitySecuritiesMember
4098 Securities Sold Under Repurchase Agreements [member] Member ck0001649373:SecuritiesSoldUnderRepurchaseAgreementsMember
4099 Short Positions in Securities and Unsettled Trades [member] Member ck0001649373:ShortPositionsInSecuritiesAndUnsettledTradesMember
4100 Short-term Deposits [member] Member ck0001649373:ShortTermDepositsMember
4101 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
4102 Structured Deposits [member] Member ck0001649373:StructuredDepositsMember
4103 Collateral and associated financial guarantees [member] Member ck0001649373:CollateralsAndGuaranteesMember
4104 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4105 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4106 Level 1 [member] Member ifrs-full:Level1OfFairValueHierarchyMember
4107 Level 2 [member] Member ifrs-full:Level2OfFairValueHierarchyMember
4108 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4109 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4110 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4111 Trading Assets [member] Member ck0001649373:TradingAssetsMember
4112 Derivative Financial Instruments [member] Member ck0001649373:DerivativeFinancialInstrumentsMember
4113 Other Financial assets at fair value through profit or loss, category [member] Member ck0001649373:OtherFinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
4114 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
4115 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
4116 Categories of financial liabilities [axis] Axis ifrs-full:CategoriesOfFinancialLiabilitiesAxis
4117 Financial liabilities, category [member] Member ifrs-full:FinancialLiabilitiesCategoryMember
4118 Trading Liabilities [member] Member ck0001649373:TradingLiabilities1Member
4119 Derivative Financial Instruments [member] Member ck0001649373:DerivativeFinancialInstrumentsMember
4120 Other financial liabilities designated at fair value through profit or loss [member] Member ck0001649373:OtherFinancialLiabilitiesDesignatedAtFairValueThroughProfitOrLossMember
4121 Disclosure of fair value measurement of assets and liabilities [line items] LineItems ck0001649373:DisclosureOfFairValueMeasurementOfAssetsAndLiabilitiesLineItems
4122 Assets at fair value Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValue
4123 Valuation technique Concept (Text/String) For Period ck0001649373:FairValuesOfFinancialInstrumentsValuationTechniqueUsed
4124 Liabilities at fair value Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValue
4125 1307 - Disclosure - Financial Instruments - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformation
4126 Implied Table Table

*

*

 implied:Table
4127 Disclosure of financial assets [abstract] Abstract ifrs-full:DisclosureOfFinancialAssetsAbstract
4128 Fair value of financial instruments transferred from Level 1 to Level 2 Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel1IntoLevel2OfFairValueHierarchyAssets
4129 Fair value of financial instruments transferred from Level 2 to Level 1 Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel2IntoLevel1OfFairValueHierarchyAssets
4130 Fair value of financial instruments transferred from Level 2 to Level 3, Derivative assets Concept (Monetary) For Period Debit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyAssets
4131 Fair value of financial instruments transferred from Level 2 to Level 3, Derivative liabilities Concept (Monetary) For Period Credit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyLiabilities
4132 Exposure to wrong-way risk Concept (Monetary) As Of Debit ck0001649373:ExposureToWrongWayRisk
4133 1308 - Disclosure - Financial Instruments - Summary of Fair Value Adjustment (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfFairValueAdjustment
4134 Disclosure of financial assets [table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
4135 Fair Value Adjustments [axis] Axis ck0001649373:FairValueAdjustmentsAxis
4136 Fair Value Adjustments [domain] Member ck0001649373:FairValueAdjustmentsDomain
4137 Bid-Offer and Trade Specific Adjustments [Member] Member ck0001649373:BidOfferAndTradeSpecificRiskRelatedAdjustmentsMember
4138 Uncertainty [Member] Member ck0001649373:RiskRelatedUncertaintyAdjustmentsMember
4139 Credit Risk Adjustment [Member] Member ck0001649373:CreditRiskAdjustmentsMember
4140 Funding Fair Value Adjustment [Member] Member ck0001649373:RiskRelatedFundingFairValueAdjustmentMember
4141 Risk Related Adjustments [Member] Member ck0001649373:RiskRelatedAdjustmentsMember
4142 Model-Related [Member] Member ck0001649373:ModelRelatedAdjustmentsMember
4143 Day One Profit [Member] Member ck0001649373:DayOneProfitAdjustmentsMember
4144 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4145 Fair value adjustments Concept (Monetary) For Period Debit ck0001649373:FairValueAdjustmentsRisk
4146 1309 - Disclosure - Financial Instruments - Analysis of Financial Instruments Valued Using Internal Models Based on Information Other Than Market Data (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsAnalysisOfFinancialInstrumentsValuedUsingInternalModelsBasedOnInformationOtherThanMarketData
4147 Disclosure of financial assets [table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
4148 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4149 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4150 Reversionary property securities [member] Member ck0001649373:ReversionaryPropertyInterestsMember
4151 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4152 Unlisted Equity Shares [member] Member ck0001649373:UnlistedEquitySharesMember
4153 Credit Linked Note [member] Member ck0001649373:CreditLinkedNoteMember
4154 Property Related Options and Forwards [Member] Member ck0001649373:PropertyRelatedOptionsAndForwardsMember
4155 Credit Protection Guarantees [member] Member ck0001649373:CreditProtectionGuaranteesMember
4156 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4157 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4158 Equity and Credit Contracts [member] Member ck0001649373:EquityAndCreditContractsMember
4159 Roll-up Mortgage Portfolio [member] Member ck0001649373:RollupMortgagePortfolioMember
4160 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
4161 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
4162 Other Loans [member] Member ck0001649373:OtherLoansMember
4163 Financial Guarantees [member] Member ck0001649373:FinancialGuaranteesMember
4164 Other Level 3 [member] Member ck0001649373:OtherLevelThreeMember
4165 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4166 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4167 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
4168 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4169 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4170 Derivative assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
4171 FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
4172 FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
4173 Derivative liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
4174 FVTPL Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLoss
4175 Financial assets and liabilities Concept (Monetary) As Of Debit ck0001649373:FinancialAssetsAndLiabilities
4176 Other Level 3 assets Concept (Monetary) As Of Debit ifrs-full:OtherFinancialAssets
4177 Other Level 3 liabilities Concept (Monetary) As Of Credit ifrs-full:OtherFinancialLiabilities
4178 Total net assets Concept (Monetary) As Of Debit ifrs-full:NetAssetsLiabilities
4179 Financial asset liabilities Concept (Monetary) For Period Debit ck0001649373:GainsLossesRecognisedInProfitOrLossFairValueMeasurementAssetsLiabilities
4180 Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss) Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementAssets
4181 Derivative liabilities and other Level 3 liabilities, fair value movements recognised in profit/(loss) Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementLiabilities
4182 Total (expense)/income Concept (Monetary) For Period Debit ck0001649373:FairValueMovementRecognisedInProfitLoss
4183 1310 - Disclosure - Financial Instruments - Liabilities Reconciliation of Fair Value Measurements in Level 3 of the Fair Value Hierarchy (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsLiabilitiesReconciliationOfFairValueMeasurementsInLevel3OfTheFairValueHierarchy
4184 Disclosure of Financial Liabilities [Table] Table

*

*

 ifrs-full:DisclosureOfFinancialLiabilitiesTable
4185 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4186 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4187 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4188 Classes of liabilities [axis] Axis ifrs-full:ClassesOfLiabilitiesAxis
4189 Liabilities [member] Member ifrs-full:LiabilitiesMember
4190 Derivative Liabilities [Member] Member ck0001649373:DerivativeLiabilitiesMember
4191 Categories of financial liabilities [axis] Axis ifrs-full:CategoriesOfFinancialLiabilitiesAxis
4192 Financial liabilities, category [member] Member ifrs-full:FinancialLiabilitiesCategoryMember
4193 Fair Value Through P&L [member] Member ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossCategoryMember
4194 Financial Liabilities at Fair Value, Class [member] Member ifrs-full:FinancialLiabilitiesAtFairValueMember
4195 Disclosure of fair value measurement of liabilities [line items] LineItems ifrs-full:DisclosureOfFairValueMeasurementOfLiabilitiesLineItems
4196 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Liabilities
4197 Adoption of IFRS 9 Concept (Monetary) For Period Credit ck0001649373:IncreaseDecreaseInFinancialLiabilities
4198 At 1 January 2018 Concept (Monetary) As Of Credit ck0001649373:LiabilitiesAfterAdoptionOfIFRS9
4199 Total (losses)/gains recognised in profit/loss, fair value movements Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementLiabilities
4200 Total (losses)/gains recognised in profit/loss, foreign exchange and other movements Concept (Monetary) For Period ck0001649373:GainsLossesRecognisedInProfitOrLossForeignExchangeAndOtherMovementsLiabilities
4201 Transfers in Concept (Monetary) For Period Credit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyLiabilities
4202 Gains recognised in other comprehensive income Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInOtherComprehensiveIncomeFairValueMeasurementLiabilities
4203 Additions Concept (Monetary) For Period Credit ifrs-full:PurchasesFairValueMeasurementLiabilities
4204 Sales Concept (Monetary) For Period Debit ifrs-full:SalesFairValueMeasurementLiabilities
4205 Settlements Concept (Monetary) For Period Debit ifrs-full:SettlementsFairValueMeasurementLiabilities
4206 Ending Balance Concept (Monetary) As Of Credit ifrs-full:Liabilities
4207 (Losses)/gains recognised in profit or loss relating to assets and liabilities held at the end of the year Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInFairValueMeasurementLiabilities
4208 1311 - Disclosure - Financial Instruments - Assets Reconciliation of Fair Value Measurements in Level 3 of the Fair Value Hierarchy (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsAssetsReconciliationOfFairValueMeasurementsInLevel3OfTheFairValueHierarchy
4209 Disclosure of financial assets [table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
4210 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4211 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4212 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4213 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4214 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4215 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
4216 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
4217 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4218 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4219 Fair Value Through P&L [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
4220 Financial assets at FVOCI [member] Member ck0001649373:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeMember
4221 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4222 Beginning balance Concept (Monetary) As Of Debit ifrs-full:Assets
4223 Adoption of IFRS 9 Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInFinancialAssets
4224 At 1 January 2018 Concept (Monetary) As Of Debit ck0001649373:AssetsAfterAdoptionOfIFRS9
4225 Total (losses)/gains recognised in profit/loss, fair value movements Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementAssets
4226 Total (losses)/gains recognised in profit/loss, foreign exchange and other movements Concept (Monetary) For Period ck0001649373:GainsLossesRecognisedInProfitOrLossForeignExchangeAndOtherMovementAssets
4227 Transfers in Concept (Monetary) For Period Debit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyAssets
4228 Gains recognised in other comprehensive income Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInOtherComprehensiveIncomeFairValueMeasurementAssets
4229 Additions Concept (Monetary) For Period Debit ifrs-full:PurchasesFairValueMeasurementAssets
4230 Sales Concept (Monetary) For Period Credit ifrs-full:SalesFairValueMeasurementAssets
4231 Settlements Concept (Monetary) For Period Credit ifrs-full:SettlementsFairValueMeasurementAssets
4232 Ending Balance Concept (Monetary) As Of Debit ifrs-full:Assets
4233 (Losses)/gains recognised in profit or loss relating to assets and liabilities held at the end of the year Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInFairValueMeasurementAssets
4234 1312 - Disclosure - Financial Instruments - Effects of Changes in Significant Unobservable Assumptions to Reasonably Possible Alternatives (Level 3) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsEffectsOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevel3
4235 Effect of changes in significant unobservable assumptions to reasonably possible alternatives - Level 3 [table] Table

*

*

 ck0001649373:EffectOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevel3Table
4236 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4237 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4238 Fair Value Through P&L [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
4239 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
4240 Available-for-Sale [member] Member ck0001649373:AvailableForSaleMember
4241 Range [axis] Axis ifrs-full:RangeAxis
4242 Ranges [member] Member ifrs-full:RangesMember
4243 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
4244 Top of Range [member] Member ifrs-full:TopOfRangeMember
4245 Weighted average [member] Member ifrs-full:WeightedAverageMember
4246 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4247 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4248 Equity and Credit Contracts [member] Member ck0001649373:EquityAndCreditContractsMember
4249 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
4250 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
4251 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4252 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
4253 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
4254 Property Related Options and Forwards [Member] Member ck0001649373:PropertyRelatedOptionsAndForwardsMember
4255 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4256 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4257 Reversionary property securities [member] Member ck0001649373:ReversionaryPropertyInterestsMember
4258 Roll-up Mortgage Portfolio [member] Member ck0001649373:RollupMortgagePortfolioMember
4259 Unlisted Equity Shares [member] Member ck0001649373:UnlistedEquitySharesMember
4260 Other Loans [member] Member ck0001649373:OtherLoansMember
4261 Effect of changes in significant unobservable assumptions to reasonably possible alternatives - Level 3 [line items] LineItems ck0001649373:EffectOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevel3LineItems
4262 Fair value Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValue
4263 Fair value Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValue
4264 Assumption description Concept (Text/String) For Period ifrs-full:ChangesInMethodsAndAssumptionsUsedInPreparingSensitivityAnalysis
4265 Assumption value Concept (Percent) For Period ck0001649373:InterestRateSignificantUnobservableInputs
4266 Shift Concept (Percent) For Period ck0001649373:ShiftInFairValueInstrument
4267 Favourable changes Concept (Monetary) For Period Credit ck0001649373:FavourableChangesInFairValue
4268 Unfavourable changes Concept (Monetary) For Period Credit ck0001649373:UnfavourableChangesInFairValue
4269 HPI spot rate index level Concept (Integer) For Period ck0001649373:HousePriceIndexSpotRateIndexLevel
4270 1313 - Disclosure - Financial Instruments - Maturities of Undiscounted Cash Flows for Financial Liabilities and Off Balance Sheet Commitments (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInstrumentsMaturitiesOfUndiscountedCashFlowsForFinancialLiabilitiesAndOffBalanceSheetCommitments
4271 Disclosure Of Maturity Analysis For Financial Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfMaturityAnalysisForFinancialLiabilitiesTable
4272 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4273 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4274 Undiscounted Cash Flow [member] Member ck0001649373:UndiscountedCashFlowMember
4275 Maturity [axis] Axis ifrs-full:MaturityAxis
4276 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
4277 On Demand [member] Member ifrs-full:OnDemandMember
4278 Not Later Than Three Months [member] Member ifrs-full:NotLaterThanThreeMonthsMember
4279 Later Than Three Months and Not Later Than One Year [member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanOneYearMember
4280 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
4281 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
4282 Disclosure Of Maturity Analysis For Financial Liabilities [line items] LineItems ck0001649373:DisclosureOfMaturityAnalysisForFinancialLiabilitiesLineItems
4283 Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
4284 Derivative financial instruments Concept (Monetary) As Of Credit ck0001649373:DerivativeFinancialLiabilitiesGross
4285 Other financial liabilities at fair value through profit or loss Concept (Monetary) As Of Credit ck0001649373:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
4286 Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
4287 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
4288 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
4289 Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
4290 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
4291 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
4292 Off-balance sheet commitments given Concept (Monetary) As Of Credit ck0001649373:OffBalanceSheetCommitments
4293 1314 - Disclosure - Offsetting Financial Assets and Liabilities - Summary of Information about Impact of Offsetting of Financial Assets and Liabilities (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOffsettingFinancialAssetsAndLiabilitiesSummaryOfInformationAboutImpactOfOffsettingOfFinancialAssetsAndLiabilities
4294 Disclosure Of Off Setting Of Financial Assets And Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfOffSettingOfFinancialAssetsAndLiabilitiesTable
4295 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4296 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4297 Derivative Financial Liabilities [member] Member ck0001649373:DerivativeFinancialLiabilitiesMember
4298 Amortised cost [member] Member ck0001649373:AmortisedCostMember
4299 Fair Value [member] Member ifrs-full:AtFairValueMember
4300 Deposits by Customers and Banks [Member] Member ck0001649373:DepositsByCustomersAndBanksMember
4301 Derivative Financial Instruments [member] Member ck0001649373:DerivativeFinancialAssetsMember
4302 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4303 Disclosure of offsetting of financial assets and liabilities [line items] LineItems ck0001649373:DisclosureOfOffSettingOfFinancialAssetsAndLiabilitiesLineItems
4304 Gross amounts, Assets Concept (Monetary) As Of Debit ifrs-full:GrossFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4305 Amounts offset, Assets Concept (Monetary) As Of Credit ifrs-full:GrossFinancialLiabilitiesSetOffAgainstFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4306 Net amounts reported on the balance sheet, Assets Concept (Monetary) As Of Debit ifrs-full:NetFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsInStatementOfFinancialPosition
4307 Financial instruments, Assets Concept (Monetary) As Of Credit ifrs-full:FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
4308 Financial collateral, Assets Concept (Monetary) As Of Credit ifrs-full:CashCollateralReceivedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
4309 Net amount, Assets Concept (Monetary) As Of Credit ifrs-full:AmountsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
4310 Assets not subject to enforceable netting arrangements, Assets Concept (Monetary) As Of Debit ck0001649373:AssetsNotSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4311 Balance sheet total, Assets Concept (Monetary) As Of Debit ifrs-full:NetFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4312 Gross amounts, Liabilities Concept (Monetary) As Of Credit ifrs-full:GrossFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4313 Amounts offset, Liabilities Concept (Monetary) As Of Debit ifrs-full:GrossFinancialAssetsSetOffAgainstFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4314 Net amounts reported on the balance sheet, Liabilities Concept (Monetary) As Of Credit ifrs-full:NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsInStatementOfFinancialPosition
4315 Financial instruments, Liabilities Concept (Monetary) As Of Debit ifrs-full:FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4316 Financial collateral, Liabilities Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4317 Net amount, Liabilities Concept (Monetary) As Of Debit ifrs-full:AmountsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4318 Assets not subject to enforceable netting arrangements, Liabilities Concept (Monetary) As Of Credit ck0001649373:LiabilitiesNotSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4319 Balance sheet total, Liabilities Concept (Monetary) As Of Credit ifrs-full:NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4320 1315 - Disclosure - Ring-Fencing - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRingFencingAdditionalInformation
4321 Implied Table Table

*

*

 implied:Table
4322 Disclosure of cost and expenses by nature [abstract] Abstract ck0001649373:DisclosureOfCostAndExpensesByNatureAbstract
4323 Total cost incurred in relation to compliance with ring-rencing legislation Concept (Monetary) For Period Debit ck0001649373:CostOfRingfencing
4324 1316 - Disclosure - Transition to IFRS 9 - Summary of Measurement Categories and Carrying Amounts of Financial Assets Determined in Accordance with IAS 39 and IFRS 9 (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransitionToIFRS9SummaryOfMeasurementCategoriesAndCarryingAmountsOfFinancialAssetsDeterminedInAccordanceWithIAS39AndIFRS9
4325 Transition to IFRS 9 [table] Table

*

*

 ck0001649373:TransitionToIFRS9Table
4326 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4327 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4328 IFRS 9 [member] Member ck0001649373:IFRS9Member
4329 IAS 39 [member] Member ck0001649373:InternationalAccountingStandardsThirtyNineMember
4330 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4331 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4332 Cash and Balances at Central Banks [member] Member ck0001649373:CashAndBalancesWithCentralBanksMember
4333 Trading Assets [member] Member ck0001649373:TradingAssetsMember
4334 Derivative Financial Instruments [member] Member ck0001649373:DerivativeFinancialAssetsMember
4335 Financial assets designated at fair value [member] Member ck0001649373:FinancialAssetsDesignatedAtFairValueMember
4336 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4337 Loans and advances to banks [member] Member ck0001649373:LoansAndAdvancesToBanksMember
4338 Reverse repurchase agreements - non-trading [member] Member ck0001649373:ReverseRepurchaseAgreementsNontradingMember
4339 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
4340 Other Assets [member] Member ifrs-full:OtherAssetsMember
4341 Other financial assets designated at fair value through profit or loss [member] Member ck0001649373:OtherFinancialAssetsDesignatedAtFairValueThroughProfitOrLossMember
4342 Measurement [axis] Axis ifrs-full:MeasurementAxis
4343 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
4344 FVOCI [member] Member ck0001649373:FVOCIMember
4345 FVTPL [member] Member ck0001649373:FVTPLMember
4346 Amortised cost [member] Member ck0001649373:AmortisedCostMember
4347 FVTPL (Mandatory) [member] Member ck0001649373:FVTPLMandatoryMember
4348 FVTPL (Designated) [member] Member ck0001649373:FVTPLDesignatedMember
4349 Other financial assets at amortised cost [member] Member ck0001649373:OtherFinancialAssetsAtAmortisedCostMember
4350 Financial assets at FVOCI [member] Member ck0001649373:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeMember
4351 FVTPL (Mandatory)1 [member] Member ck0001649373:FVTPLMandatory1Member
4352 Amortised cost1 [member] Member ck0001649373:AmortisedCost1Member
4353 FVTPL (Mandatory)2 [member] Member ck0001649373:FVTPLMandatory2Member
4354 Loans and receivable securities [member] Member ck0001649373:LoansAndReceivablesMember
4355 FVTPL (Trading) [member] Member ck0001649373:FVTPLTradingMember
4356 FVTPL1 (Designated) [member] Member ck0001649373:FVTPLDesignated1Member
4357 FVTPL2 (Designated) [member] Member ck0001649373:FVTPLDesignated2Member
4358 Loans and receivable securities1 [member] Member ck0001649373:LoansAndReceivables1Member
4359 Loans and receivable securities2 [member] Member ck0001649373:LoansAndReceivables2Member
4360 Available for sale financial assets [member] Member ck0001649373:AvailableForSaleFinancialAssetsMember
4361 Available for sale financial assets1 [member] Member ck0001649373:AvailableForSaleFinancialAssets1Member
4362 Held to maturity investments [member] Member ck0001649373:HeldToMaturityInvestmentsMember
4363 Available for sale financial assets2 [member] Member ck0001649373:AvailableForSaleFinancialAssets2Member
4364 Transition to IFRS 9 [line items] LineItems ck0001649373:TransitionToIFRS9LineItems
4365 Re-classifications Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
4366 Re-measurement Concept (Monetary) For Period Debit ck0001649373:AdjustmentForAdoptionOfIFRS9AllowanceAccountForCreditLossesOfFinancialAssets
4367 Ending balance before re-presentation Concept (Monetary) As Of Debit ck0001649373:AssetsBeforeRepresentation
4368 Re-presentation Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsCarryingAmountImmediatelyAfterInitialApplicationOfIFRS9
4369 Beginning balance Concept (Monetary) As Of Debit ifrs-full:Assets
4370 1317 - Disclosure - Transition to IFRS 9 - Summary of Measurement Categories and Carrying Amounts of Financial Assets Determined in Accordance with IAS 39 and IFRS 9 (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransitionToIFRS9SummaryOfMeasurementCategoriesAndCarryingAmountsOfFinancialAssetsDeterminedInAccordanceWithIAS39AndIFRS9Parenthetical
4371 Transition to IFRS 9 [table] Table

*

*

 ck0001649373:TransitionToIFRS9Table
4372 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4373 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4374 Provisions for off-balance sheet exposures (IAS 37/IFRS 9) [member] Member ck0001649373:ProvisionsForOffbalanceSheetExposuresMember
4375 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4376 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4377 Financial guarantee contracts [member] Member ifrs-full:FinancialGuaranteeContractsMember
4378 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4379 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4380 Loans and Advances to Customers [member] Member ck0001649373:LoansAndAdvancesToCustomersMember
4381 Financial investments [member] Member ck0001649373:FinancialInvestmentsMember
4382 Legal entity [axis] Axis dei:LegalEntityAxis
4383 Entity [Domain] Member dei:EntityDomain
4384 Santander UK Group [member] Member ck0001649373:SantanderUKGroupMember
4385 Measurement [axis] Axis ifrs-full:MeasurementAxis
4386 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
4387 FVOCI [member] Member ck0001649373:FVOCIMember
4388 FVTPL [member] Member ck0001649373:FVTPLMember
4389 Amortised cost [member] Member ck0001649373:AmortisedCostMember
4390 Available-for-Sale [member] Member ck0001649373:AvailableForSaleMember
4391 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4392 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4393 IFRS 9 [member] Member ck0001649373:IFRS9Member
4394 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
4395 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
4396 Allowance for credit losses [member] Member ifrs-full:AllowanceForCreditLossesMember
4397 Reclassifications [member] Member ck0001649373:ReclassificationsMember
4398 Remeasurements [member] Member ck0001649373:RemeasurementsMember
4399 Transition to IFRS 9 [line items] LineItems ck0001649373:TransitionToIFRS9LineItems
4400 Re-measurement Concept (Monetary) For Period Debit ck0001649373:AdjustmentForAdoptionOfIFRS9AllowanceAccountForCreditLossesOfFinancialAssets
4401 Increase in deferred tax asset Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInDeferredTaxLiabilityAsset
4402 Financial assets at FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
4403 Trading assets Concept (Monetary) As Of Debit ck0001649373:TradingAssets
4404 Financial assets at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
4405 Downward remeasurement of loans and receivables Concept (Monetary) For Period Debit ck0001649373:DownwardRemeasurementOfLoansAndReceivables
4406 Downward remeasurement of financial asset Concept (Monetary) For Period Debit ck0001649373:DownwardRemeasurementOfFinancialAssets
4407 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
4408 Other financial assets at FVTPL Concept (Monetary) As Of Debit ifrs-full:OtherFinancialAssets
4409 Financial investments Concept (Monetary) As Of Debit ck0001649373:FinancialInvestments
4410 1318 - Disclosure - Transition to IFRS 9 - Disclosure of Statutory Balance Sheet Reconciliation under IAS 39 and IFRS 9 (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransitionToIFRS9DisclosureOfStatutoryBalanceSheetReconciliationUnderIAS39AndIFRS9
4411 Disclosure of financial assets [table] Table

*

*

 ifrs-full:DisclosureOfFinancialAssetsTable
4412 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4413 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4414 IFRS 9 [member] Member ck0001649373:IFRS9Member
4415 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4416 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4417 Financial Assets at Amortised Cost, Category [member] Member ifrs-full:FinancialAssetsAtAmortisedCostCategoryMember
4418 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4419 To amortised cost from FVPTL Concept (Monetary) For Period Credit ifrs-full:GainLossArisingFromDerecognitionOfFinancialAssetsMeasuredAtAmortisedCost
4420 Fair value gain that would have been recognised during the year if the financial asset had not been reclassified Concept (Monetary) For Period Credit ifrs-full:FairValueGainsOrLossThatWouldHaveBeenRecognisedInProfitOrLossIfFinancialAssetsHadNotBeenReclassified
4421 1319 - Disclosure - Transition to IFRS 9 - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureTransitionToIFRS9AdditionalInformation
4422 Transition to IFRS 9 [table] Table

*

*

 ck0001649373:TransitionToIFRS9Table
4423 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4424 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4425 IFRS 9 [member] Member ck0001649373:IFRS9Member
4426 Transition to IFRS 9 [line items] LineItems ck0001649373:TransitionToIFRS9LineItems
4427 Effective interest rate Concept (Percent) As Of ifrs-full:EffectiveInterestRateOfFinancialAssetsReclassifiedOutOfFinancialAssetsAtFairValueThroughProfitOrLoss
4428 Interest income recognized Concept (Monetary) For Period Credit ifrs-full:InterestIncomeExpenseRecognisedForFinancialAssetsReclassifiedIntoMeasuredAtAmortisedCostFirstApplicationOfIFRS9
4429 1320 - Disclosure - Events After the Balance Sheet Date - Additional Information (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureEventsAfterTheBalanceSheetDateAdditionalInformation
4430 Implied Table Table

*

*

 implied:Table
4431 Disclosure of non-adjusting events after reporting period [abstract] Abstract ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodAbstract
4432 Description of nature of Non adjusting event after reporting period Concept (Text/String) For Period ifrs-full:DescriptionOfNatureOfNonadjustingEventAfterReportingPeriod
4433 Estimated investment to refurbish 100 branches Concept (Monetary) For Period Debit ck0001649373:EstimatedInvestmentToRefurbishBranchNetwork
4434 Number of branches being closed Concept (Integer) For Period ck0001649373:NumberOfBranchesBeingClosed
4435 Number of branches in our future branch network Concept (Integer) For Period ck0001649373:NumberOfBranchesInOurFutureBranchNetwork
4436 1321 - Disclosure - Financial Statements - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialStatementsAdditionalInformationParent
4437 Statement of financial statements [table] Table

*

*

 ck0001649373:StatementOfFinancialStatementsTable
4438 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4439 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4440 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4441 Condensed Financial Statements, Captions [Line Items] LineItems srt:CondensedFinancialStatementsCaptionsLineItems
4442 Profit after tax attributable to shareholders Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
4443 Profit after tax attributable to shareholders, dividend receipts Concept (Monetary) For Period Debit ifrs-full:DividendsPaidOrdinaryShares
4444 1322 - Disclosure - Operating Expenses Before Impairment Losses, Provisions and Charges - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOperatingExpensesBeforeImpairmentLossesProvisionsAndChargesAdditionalInformationParent
4445 Disclosure Of Operating Expense [table] Table

*

*

 ck0001649373:DisclosureOfOperatingExpenseTable
4446 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4447 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4448 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4449 Disclosure Of Operating Expense [line items] LineItems ck0001649373:DisclosureOfOperatingExpenseLineItems
4450 Wages and salaries Concept (Monetary) For Period Debit ifrs-full:WagesAndSalaries
4451 Number of full-time staff Concept (Decimal) As Of ifrs-full:NumberOfEmployees
4452 1323 - Disclosure - Loans and Advances to Banks - Summary of Loans and Advances to Banks - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToBanksSummaryOfLoansAndAdvancesToBanksParent
4453 Disclosure of loans and advances to banks [table] Table

*

*

 ck0001649373:DisclosureOfLoansAndAdvancesToBanksTable
4454 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4455 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4456 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4457 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4458 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4459 Placements with Other Banks [member] Member ck0001649373:PlacementsWithOtherBanksMember
4460 Amounts Due from Santander UK Group Undertakings [member] Member ck0001649373:DueFromParentMember
4461 Disclosure of loans and advances to banks [line items] LineItems ck0001649373:DisclosureOfLoansAndAdvancesToBanksLineItems
4462 Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
4463 1324 - Disclosure - Loans and Advances to Banks - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureLoansAndAdvancesToBanksAdditionalInformationParent
4464 Disclosure of loans and advances to banks [table] Table

*

*

 ck0001649373:DisclosureOfLoansAndAdvancesToBanksTable
4465 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4466 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4467 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4468 Disclosure of loans and advances to banks [line items] LineItems ck0001649373:DisclosureOfLoansAndAdvancesToBanksLineItems
4469 Impairment losses Concept (Monetary) For Period Debit ifrs-full:ImpairmentLoss
4470 1325 - Disclosure - Other Financial Assets At Amortised Cost - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureOtherFinancialAssetsAtAmortisedCostAdditionalInformationParent
4471 Financial Assets At Fair Value Through Profit Or Loss [table] Table

*

*

 ck0001649373:FinancialAssetsAtFairValueThroughProfitOrLossTable
4472 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4473 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4474 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4475 Maturity [axis] Axis ifrs-full:MaturityAxis
4476 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
4477 Later than 10 years [member] Member ifrs-full:LaterThanTenYearsMember
4478 Financial Assets At Fair Value Through Profit Or Loss [line items] LineItems ck0001649373:FinancialAssetsAtFairValueThroughProfitOrLossLineItems
4479 Maturity of financial investments Concept (xbrli:durationItemType) For Period ck0001649373:InvestmentsMaturityPeriod
4480 1326 - Disclosure - Financial Investments - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureFinancialInvestmentsAdditionalInformationParent
4481 Disclosure Of Financial Assets And Liabilities [table] Table

*

*

 ck0001649373:DisclosureOfFinancialAssetsAndLiabilitiesTable
4482 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4483 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4484 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4485 Maturity [axis] Axis ifrs-full:MaturityAxis
4486 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
4487 Later than 10 years [member] Member ifrs-full:LaterThanTenYearsMember
4488 Disclosure of financial investments [line items] LineItems ck0001649373:DisclosureOfFinancialInvestmentsLineItems
4489 Maturity of financial investments Concept (xbrli:durationItemType) For Period ck0001649373:InvestmentsMaturityPeriod
4490 1327 - Disclosure - Interests in Other Entities - Summary of Interest in Other Entities - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesSummaryOfInterestInOtherEntitiesParent
4491 Disclosure of joint ventures [table] Table

*

*

 ifrs-full:DisclosureOfJointVenturesTable
4492 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4493 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4494 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4495 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
4496 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
4497 Fellow Subsidiaries [member] Member ifrs-full:SubsidiariesMember
4498 500m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:FiveHundredMillionFixedRateResetPerpetualATOneCapitalSecuritiesMember
4499 750m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001649373:SevenHundredAndFiftyMillionFixedRatePerpetualATOneCapitalSecuritiesMember
4500 300m Perpetual Capital Securities [member] Member ck0001649373:ThreeHundredMillionPerpetualCapitalSecuritiesMember
4501 500m Perpetual Capital Securities [member] Member ck0001649373:FiveHundredMillionPerpetualCapitalSecuritiesMember
4502 Classes of Share Capital [Axis] Axis ifrs-full:ClassesOfShareCapitalAxis
4503 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
4504 Ordinary Share Capital [member] Member ifrs-full:OrdinarySharesMember
4505 Disclosure of interest in other entities [line items] LineItems ck0001649373:DisclosureOfInterestInOtherEntitiesLineItems
4506 Interests in other entities Concept (Monetary) As Of Debit ck0001649373:DisclosureOfInterestInOtherEntities
4507 1328 - Disclosure - Interests in Other Entities - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestsInOtherEntitiesAdditionalInformationParent
4508 Disclosure of joint ventures [table] Table

*

*

 ifrs-full:DisclosureOfJointVenturesTable
4509 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4510 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4511 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4512 Business combinations [axis] Axis ifrs-full:BusinessCombinationsAxis
4513 Entity's total for business combinations [member] Member ifrs-full:EntitysTotalForBusinessCombinationsMember
4514 Santander Equity Investments Limited [member] Member ck0001649373:SantanderEquityInvestmentsLimitedMember
4515 Abbey national treasury services plc [member] Member ck0001649373:AbbeyNationalTreasuryServicesPlcMember
4516 Disclosure of subsidiaries [line items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
4517 Impairment loss Concept (Monetary) For Period Debit ifrs-full:ImpairmentLoss
4518 Number of associates Concept (Integer) For Period ck0001649373:NumberOfAssociates
4519 Ownership interest in share capital Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInSubsidiary
4520 Percentage of share capital acquired Concept (Percent) As Of ifrs-full:PercentageOfVotingEquityInterestsAcquired
4521 Consideration of acquisition equal to book value of the associated assets and liabilities Concept (Monetary) As Of Credit ifrs-full:AcquisitiondateFairValueOfTotalConsiderationTransferred
4522 1329 - Disclosure - Interest in other entities - Summary of interests in subsidiaries (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureInterestInOtherEntitiesSummaryOfInterestsInSubsidiaries
4523 Disclosure of subsidiaries [table] Table

*

*

 ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
4524 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
4525 Carrying amount [member] Member ifrs-full:CarryingAmountMember
4526 Cost [member] Member ifrs-full:GrossCarryingAmountMember
4527 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4528 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4529 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4530 Disclosure of subsidiaries [line items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
4531 At 1 January 2017, 31 December 2017 and 1 January 2018 Concept (Monetary) As Of Debit ifrs-full:InvestmentsInSubsidiaries
4532 Additions Concept (Monetary) For Period Debit ck0001649373:IncreaseThroughAdditionsInvestmentsInSubsidiaries
4533 At 31 December 2018 Concept (Monetary) As Of Debit ifrs-full:InvestmentsInSubsidiaries
4534 1330 - Disclosure - Subordinated Liabilities - Summary of Subordinated Liabilities - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfSubordinatedLiabilitiesParent
4535 Subordinated Liabilities [table] Table

*

*

 ck0001649373:SubordinatedLiabilitiesTable
4536 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
4537 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
4538 4.75% Subordinated Notes 2025 [member] Member ck0001649373:FourPointSevenFivePercentSubordinatedNotesTwentyTwentyFiveMember
4539 5.625% Subordinated Notes 2045 [member] Member ck0001649373:FivePointSixTwoFivePercentSubordinatedNotesTwentyFortyFiveMember
4540 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4541 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4542 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4543 Subordinated liabilities [line items] LineItems ck0001649373:SubordinatedLiabilitiesLineItems
4544 Borrowings maturity Concept (Text/String) For Period ifrs-full:BorrowingsMaturity
4545 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
4546 1331 - Disclosure - Subordinated Liabilities - Summary of Subordinated Liabilities - Parent (Parenthetical) (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfSubordinatedLiabilitiesParentParenthetical
4547 Subordinated Liabilities [table] Table

*

*

 ck0001649373:SubordinatedLiabilitiesTable
4548 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
4549 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
4550 4.75% Subordinated Notes 2025 [member] Member ck0001649373:FourPointSevenFivePercentSubordinatedNotesTwentyTwentyFiveMember
4551 5.625% Subordinated Notes 2045 [member] Member ck0001649373:FivePointSixTwoFivePercentSubordinatedNotesTwentyFortyFiveMember
4552 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4553 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4554 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4555 Subordinated liabilities [line items] LineItems ck0001649373:SubordinatedLiabilitiesLineItems
4556 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
4557 Notional amount Concept (Monetary) As Of Credit ck0001649373:SubordinatedNotesNotionalAmount
4558 1332 - Disclosure - Changes in Liabilities Arising From Financing Activities - Summary of Changes in Liabilities Arising from Financing Activities - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureChangesInLiabilitiesArisingFromFinancingActivitiesSummaryOfChangesInLiabilitiesArisingFromFinancingActivitiesParent
4559 Disclosure of reconciliation of liabilities arising from financing activities [table] Table

*

*

 ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesTable
4560 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4561 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4562 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4563 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4564 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4565 Debt Securities [member] Member ck0001649373:DebtSecuritiesInIssueMember
4566 Subordinated liabilities [member] Member ck0001649373:SubordinatedLiabilitiesMember
4567 Other Equity Instruments [member] Member ifrs-full:OtherEquityInterestMember
4568 Dividends Paid [member] Member ck0001649373:DividendsPaidMember
4569 Disclosure of reconciliation of liabilities arising from financing activities [line items] LineItems ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesLineItems
4570 Beginning Balance Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
4571 Cash flows from financing activities Concept (Monetary) For Period ck0001649373:CashFlowsFromUsedInFinancingActivitiesArisingFromChangeInLiabilitiesOfFinancing
4572 Cash flows from operating activities Concept (Monetary) For Period ck0001649373:CashFlowsFromUsedInOperatingActivitiesArisingFromChangeInLiabilitiesOfFinancing
4573 - Unrealised foreign exchange Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughEffectOfChangesInForeignExchangeRatesLiabilitiesArisingFromFinancingActivities
4574 - Other changes Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughOtherChangesLiabilitiesArisingFromFinancingActivities
4575 Ending Balance Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
4576 1333 - Disclosure - Related Party Transactions - Additional Information - Parent (Detail) Network

*

*

 http://santander.co.uk/taxonomy/role/DisclosureRelatedPartyTransactionsAdditionalInformationParent
4577 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
4578 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
4579 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
4580 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
4581 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
4582 Description related party transactions Concept (Text/String) For Period ifrs-full:DescriptionOfTransactionsWithRelatedParty

*

*