SANTANDER UK 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

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http://imetrix.edgar-online.com/taxonomy/role/DocumentandEntityInformation
2 Implied Table Table

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implied:Table
3 Document and entity information [abstract] Abstract ck0001087711: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

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http://imetrix.edgar-online.com/taxonomy/role/NotesAnalysisOfIncomeAndExpense-800200
20 Implied Table Table

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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 ck0001087711: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 ck0001087711: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 ck0001087711:ProvisionsForOtherLiabilitiesAndCharges
34 Total operating credit impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001087711: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

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http://imetrix.edgar-online.com/taxonomy/role/StatementOfComprehensiveIncomeOCIComponentsPresentedNetOfTax-410000
43 Implied Table Table

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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 ck0001087711: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 ck0001087711: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

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http://imetrix.edgar-online.com/taxonomy/role/StatementOfFinancialPositionOrderOfLiquidity-220000
82 Implied Table Table

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implied:Table
83 Statement of financial position [abstract] Abstract ifrs-full:StatementOfFinancialPositionAbstract
84 Assets Abstract ifrs-full:AssetsAbstract
85 Cash and balances at central banks Concept (Monetary) As Of Debit ifrs-full:CashAndBankBalancesAtCentralBanks
86 Financial assets at fair value through profit or loss: Abstract ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossAbstract
87 - Trading assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
88 - Derivative financial instruments Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
89 - Other financial assets at fair value through profit or loss Concept (Monetary) As Of Debit ck0001087711:OtherFinancialAssetsAtFairValueThroughProfitOrLoss
90 Financial assets at amortised cost: Abstract ck0001087711:FinancialAssetsAtAmortisedCostAbstract
91 - Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
92 - Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
93 - Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
94 - Other financial assets at amortised cost Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtAmortisedCost
95 Financial assets at fair value through other comprehensive income Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
96 Financial investments Concept (Monetary) As Of Debit ck0001087711:FinancialInvestments
97 Interests in other entities Concept (Monetary) As Of Debit ifrs-full:InvestmentsInSubsidiariesJointVenturesAndAssociates
98 Intangible assets Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsAndGoodwill
99 Property, plant and equipment Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
100 Current tax assets Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssets
101 Retirement benefit assets Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsDefinedBenefitPlan
102 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
103 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
104 Liabilities Abstract ifrs-full:LiabilitiesAbstract
105 Financial liabilities at fair value through profit or loss: Abstract ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossAbstract
106 - Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
107 - Derivative financial instruments Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
108 - Other financial liabilities at fair value through profit or loss Concept (Monetary) As Of Credit ck0001087711:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
109 Financial liabilities at amortised cost: Abstract ck0001087711:FinancialLiabilitiesAtAmortisedCostAbstract
110 - Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
111 - Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
112 - Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
113 - Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
114 - Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
115 Other liabilities Concept (Monetary) As Of Credit ifrs-full:OtherLiabilities
116 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
117 Current tax liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilities
118 Deferred tax liabilities Concept (Monetary) As Of Credit ifrs-full:NetDeferredTaxLiabilities
119 Retirement benefit obligations Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
120 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
121 Equity Abstract ifrs-full:EquityAbstract
122 Share capital Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
123 Share premium Concept (Monetary) As Of Credit ifrs-full:SharePremium
124 Other equity instruments Concept (Monetary) As Of Credit ifrs-full:OtherEquityInterest
125 Retained earnings Concept (Monetary) As Of Credit ifrs-full:RetainedEarnings
126 Other reserves Concept (Monetary) As Of Credit ifrs-full:OtherReserves
127 Total shareholders' equity Concept (Monetary) As Of Credit ifrs-full:EquityAttributableToOwnersOfParent
128 Non-controlling interests Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
129 Total equity Concept (Monetary) As Of Credit ifrs-full:Equity
130 Total liabilities and equity Concept (Monetary) As Of Credit ifrs-full:EquityAndLiabilities
131 1006 - Statement - Consolidated Cash Flow Statement Network

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http://imetrix.edgar-online.com/taxonomy/role/StatementOfCashFlowsIndirectMethod-520000
132 Implied Table Table

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implied:Table
133 Statement of cash flows [abstract] Abstract ifrs-full:StatementOfCashFlowsAbstract
134 Cash flows from operating activities Abstract ifrs-full:CashFlowsFromUsedInOperatingActivitiesAbstract
135 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
136 Non-cash items included in profit: Abstract ifrs-full:AdjustmentsForReconcileProfitLossAbstract
137 - Depreciation and amortisation Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDepreciationAndAmortisationExpense
138 - Provisions for other liabilities and charges Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForProvisions
139 - Impairment losses Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLoss
140 - Corporation tax charge Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncomeTaxExpense
141 - Other non-cash items Concept (Monetary) For Period Debit ifrs-full:OtherAdjustmentsForNoncashItems
142 - Pension charge for defined benefit pension schemes Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForPensionChargeForDefinedBenefitPensionSchemes
143 Adjustments to reconcile profit (loss) Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForReconcileProfitLoss
144 Net change in operating assets and liabilities: Abstract ck0001087711:ChangeInOperatingAssetsAndLiabilitiesAbstract
145 - Cash and balances at central banks Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForDecreaseIncreaseInCashAndBalancesAtCentralBanks
146 - Trading assets Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForDecreaseIncreaseInTradingAssets
147 - Derivative assets Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForIncreaseDecreaseInDerivativeAssets
148 - Other financial assets at fair value through profit or loss Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForDecreaseIncreaseInOtherFinancialAssetsAtFairValueThroughProfitOrLoss
149 - Loans and advances to banks and customers Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForDecreaseIncreaseInLoansAndAdvancesToBanksAndCustomers
150 - Other assets Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInOtherAssets
151 - Deposits by banks and customers Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForIncreaseDecreaseInDepositsFromBanksAndCustomers
152 - Derivative liabilities Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForIncreaseDecreaseInDerivativeLiabilities
153 - Trading liabilities Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForIncreaseDecreaseInTradingLiabilities
154 - Other financial liabilities at fair value through profit or loss Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForIncreaseDecreaseInOtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
155 - Debt securities in issue Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForIncreaseDecreaseInDebtSecuritiesInIssue
156 - Other liabilities Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInOtherLiabilities
157 Net change in operating assets and liabilities Concept (Monetary) For Period Debit ck0001087711:AdjustmentsForDecreaseIncreaseInOperatingAssetsAndLiabilities
158 Corporation taxes paid Concept (Monetary) For Period Credit ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities
159 Effects of exchange rate differences Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForUnrealisedForeignExchangeLossesGains
160 Net cash flows from operating activities Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperatingActivities
161 Cash flows from investing activities Abstract ifrs-full:CashFlowsFromUsedInInvestingActivitiesAbstract
162 Investments in other entities Concept (Monetary) For Period Credit ifrs-full:CashFlowsUsedInObtainingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
163 Proceeds from disposal of subsidiaries Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
164 Purchase of property, plant and equipment and intangible assets Concept (Monetary) For Period Credit ifrs-full:PurchaseOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
165 Proceeds from sale of property, plant and equipment and intangible assets Concept (Monetary) For Period Debit ifrs-full:ProceedsFromDisposalsOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
166 Purchase of financial investments Concept (Monetary) For Period Credit ck0001087711:PurchasesOfFinancialInvestments
167 Proceeds from sale and redemption of financial investments Concept (Monetary) For Period Debit ck0001087711:ProceedsFromDisposalOrMaturityOfFinancialInvestments
168 Net cash flows from investing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInInvestingActivities
169 Cash flows from financing activities Abstract ifrs-full:CashFlowsFromUsedInFinancingActivitiesAbstract
170 Issue of AT1 Capital Securities Concept (Monetary) For Period Debit ifrs-full:ProceedsFromIssuingOtherEquityInstruments
171 Issuance costs of AT1 Capital Securities Concept (Monetary) For Period Credit ck0001087711:PaymentForOtherEquityInstrumentsIssueCosts
172 Issue of debt securities and subordinated notes Concept (Monetary) For Period Debit ifrs-full:ProceedsFromIssueOfBondsNotesAndDebentures
173 Issuance costs of debt securities and subordinated notes Concept (Monetary) For Period Credit ifrs-full:PaymentsForDebtIssueCosts
174 Repayment of debt securities and subordinated notes Concept (Monetary) For Period Credit ifrs-full:RepaymentsOfBondsNotesAndDebentures
175 Repurchase of preference shares and other equity instruments Concept (Monetary) For Period Credit ck0001087711:PaymentsForRepurchaseOfPreferenceSharesAndOtherEquityInstruments
176 Dividends paid on ordinary shares Concept (Monetary) For Period Credit ifrs-full:DividendsPaidClassifiedAsFinancingActivities
177 Dividends paid on preference shares and other equity instruments Concept (Monetary) For Period Credit ck0001087711:DividendsPaidOnPreferenceSharesAndOtherEquityInstrumentsClassifiedAsFinancingActivities
178 Dividends paid on non-controlling interests Concept (Monetary) For Period Credit ifrs-full:DividendsPaidToNoncontrollingInterestsClassifiedAsFinancingActivities
179 Net cash flows from financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
180 Change in cash and cash equivalents Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInCashAndCashEquivalentsBeforeEffectOfExchangeRateChanges
181 Cash and cash equivalents at beginning of the year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition
182 Effects of exchange rate changes on cash and cash equivalents Concept (Monetary) For Period Debit ifrs-full:EffectOfExchangeRateChangesOnCashAndCashEquivalents
183 Cash and cash equivalents at the end of the year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition
184 Cash and cash equivalents consist of: Abstract ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPositionAbstract
185 Cash and balances at central banks Concept (Monetary) As Of Debit ifrs-full:CashAndBankBalancesAtCentralBanks
186 Less: regulatory minimum cash balances Concept (Monetary) As Of Debit ifrs-full:MandatoryReserveDepositsAtCentralBanks
187 Cash and bank balances at central banks less regulatory minimum cash balances Concept (Monetary) As Of Debit ifrs-full:BankBalancesAtCentralBanksOtherThanMandatoryReserveDeposits
188 Net trading other cash equivalents Concept (Monetary) As Of Debit ck0001087711:NetTradingAndOtherCashEquivalents
189 Net non-trading other cash equivalents Concept (Monetary) As Of Debit ck0001087711:NetNonTradingOtherCashEquivalents
190 Cash and cash equivalents at the end of the year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition
191 Cash flows from investing activities Abstract ifrs-full:CashFlowsFromUsedInInvestingActivitiesAbstract
192 Investments in other entities Concept (Monetary) For Period Credit ifrs-full:CashFlowsUsedInObtainingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
193 Proceeds from disposal of subsidiaries Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
194 Purchase of property, plant and equipment and intangible assets Concept (Monetary) For Period Credit ifrs-full:PurchaseOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
195 Proceeds from sale of property, plant and equipment and intangible assets Concept (Monetary) For Period Debit ifrs-full:ProceedsFromDisposalsOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
196 Purchase of financial investments Concept (Monetary) For Period Credit ck0001087711:PurchasesOfFinancialInvestments
197 Proceeds from sale and redemption of financial investments Concept (Monetary) For Period Debit ck0001087711:ProceedsFromDisposalOrMaturityOfFinancialInvestments
198 Net cash flows from investing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInInvestingActivities
199 1007 - Statement - Consolidated Cash Flow Statement (Parenthetical) Network

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http://imetrix.edgar-online.com/taxonomy/role/StatementOfCashFlowsIndirectMethod-520000Parenthetical
200 Implied Table Table

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implied:Table
201 Statement of cash flows [abstract] Abstract ifrs-full:StatementOfCashFlowsAbstract
202 Cash consideration received on sale of subsidiaries Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
203 Carrying value of assets and liabilities Concept (Monetary) For Period Debit ck0001087711:CarryingValueOfAssetsAndLiabilitiesOtherThanCashOrCashEquivalentsInSubsidiary
204 1008 - Statement - Consolidated Statement of Changes in Equity Network

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http://imetrix.edgar-online.com/taxonomy/role/StatementOfChangesInEquity-610000
205 Statement of changes in equity [table] Table

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ifrs-full:StatementOfChangesInEquityTable
206 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
207 Equity [member] Member ifrs-full:EquityMember
208 Share Capital [member] Member ifrs-full:IssuedCapitalMember
209 Share premium [member] Member ifrs-full:SharePremiumMember
210 Other Equity Instruments [member] Member ifrs-full:OtherEquityInterestMember
211 Other Reserves Available-For-Sale [member] Member ifrs-full:ReserveOfGainsAndLossesOnRemeasuringAvailableforsaleFinancialAssetsMember
212 Other Reserves Fair Value Reserves [member] Member ifrs-full:ReserveOfGainsAndLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember
213 Other Reserves Cash Flow Hedging [member] Member ifrs-full:ReserveOfCashFlowHedgesMember
214 Other Reserves Currency Translation [member] Member ifrs-full:ReserveOfExchangeDifferencesOnTranslationMember
215 Retained Earnings [member] Member ifrs-full:RetainedEarningsMember
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 ck0001087711: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 other equity instruments Concept (Monetary) For Period Debit ck0001087711:RepurchaseOfOtherEquityInstruments
233 Dividends on ordinary shares Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToOwnersOfParent
234 Dividends on preference shares and other equity instruments Concept (Monetary) For Period Debit ck0001087711:DividendsOnPreferenceSharesAndOtherEquityInstruments
235 Dividends on non-controlling interests Concept (Monetary) For Period Debit ifrs-full:DividendsRecognisedAsDistributionsToNoncontrollingInterests
236 Tax on other equity instruments Concept (Monetary) For Period Debit ck0001087711:TaxOnOtherEquityInstruments
237 Ending balance Concept (Monetary) As Of Credit ifrs-full:Equity
238 1009 - Disclosure - Risk Framework Network

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http://imetrix.edgar-online.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialRiskManagementExplanatory
239 Implied Table Table

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240 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
241 Risk Framework Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialRiskManagementExplanatory
242 1010 - Disclosure - Credit risk Network

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http://imetrix.edgar-online.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCreditRiskExplanatory
243 Implied Table Table

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implied:Table
244 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
245 Credit risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCreditRiskExplanatory
246 1011 - Disclosure - Market risk Network

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http://imetrix.edgar-online.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfMarketRiskExplanatory
247 Implied Table Table

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248 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
249 Market risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfMarketRiskExplanatory
250 1012 - Disclosure - Liquidity risk Network

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254 1013 - Disclosure - Capital risk Network

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257 Capital risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCapitalRiskExplanatory
258 1014 - Disclosure - Accounting Policies Network

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261 Accounting Policies Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
262 1015 - Disclosure - Segments Network

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265 Segments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEntitysReportableSegmentsExplanatory
266 1016 - Disclosure - Net Interest Income Network

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269 Net Interest Income Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestIncomeExpenseExplanatory
270 1017 - Disclosure - Net Fee and Commission Income Network

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273 Net Fee and Commission Income Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFeeAndCommissionIncomeExpenseExplanatory
274 1018 - Disclosure - Net Trading and Other Income Network

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277 Net Trading and Other Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfTradingIncomeExpenseAndOtherOperatingIncomeExpenseExplanatory
278 1019 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges Network

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281 Operating Expenses Before Credit Impairment Losses, Provisions and Charges Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfExpensesExplanatory
282 1020 - Disclosure - Audit and Other Services Network

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285 Audit and Other Services Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAuditorsRemunerationExplanatory
286 1021 - Disclosure - Credit Impairment Losses and Provisions Network

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289 Credit Impairment Losses and Provisions Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfImpairmentLossesOnFinancialAssetsAndProvisionsExplanatory
290 1022 - Disclosure - Taxation Network

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293 Taxation Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfIncomeTaxAndDeferredTaxesExplanatory
294 1023 - Disclosure - Dividends on Ordinary Shares Network

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297 Dividends on Ordinary Shares Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDividendsExplanatory
298 1024 - Disclosure - Trading Assets Network

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300 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
301 Trading Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsHeldForTradingExplanatory
302 1025 - Disclosure - Derivative Financial Instruments Network

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305 Derivative Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDerivativeFinancialInstrumentsExplanatory
306 1026 - Disclosure - Other Financial Assets At Fair Value Through Profit Or Loss Network

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309 Other Financial Assets At Fair Value Through Profit Or Loss Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatory
310 1027 - Disclosure - Loans and Advances to Customers Network

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313 Loans and Advances to Customers Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfLoansAndAdvancesToCustomersExplanatory
314 1028 - Disclosure - Securitisations and Covered Bonds Network

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317 Securitisations and Covered Bonds Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfSecuritisationsAndCoveredBondsExplanatory
318 1029 - Disclosure - Transfers of Financial Assets Not Qualifying for Derecognition Network

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321 Transfers of Financial Assets Not Qualifying for Derecognition Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialAssetsTransferredDuringPeriodWhichDoNotQualifyForDerecognitionExplanatory
322 1030 - Disclosure - Reverse Repurchase Agreements - Non Trading Network

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323 Statement [table] Table

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324 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
325 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
326 Reverse repurchase agreements - non-trading [member] Member ck0001087711:ReverseRepurchaseAgreementsNontradingMember
327 Statement [LineItems] LineItems ck0001087711:StatementLineItems
328 Reverse Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfReverseRepurchaseAgreementsNontradingExplanatory
329 1031 - Disclosure - Other Financial Assets At Amortised Cost Network

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332 Other Financial Assets At Amortised Cost Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherFinancialAssetsAtAmortisedCostExplanatory
333 1032 - Disclosure - Financial Assets At Fair Value Through Other Comprehensive Income Network

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336 Financial Assets At Fair Value Through Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatory
337 1033 - Disclosure - Financial Investments Network

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340 Financial Investments Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfFinancialInvestmentsExplanatory
341 1034 - Disclosure - Interests in Other Entities Network

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343 Investments accounted for using equity method [abstract] Abstract ifrs-full:InvestmentsAccountedForUsingEquityMethodAbstract
344 Interests in Other Entities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestsInOtherEntitiesExplanatory
345 1035 - Disclosure - Intangible Assets Network

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347 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
348 Intangible Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIntangibleAssetsAndGoodwillExplanatory
349 1036 - Disclosure - Trading Liabilities Network

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352 Trading Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialLiabilitiesHeldForTradingExplanatory
353 1037 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss Network

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356 Other Financial Liabilities at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossExplanatory
357 1038 - Disclosure - Deposits by Customers Network

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360 Deposits by Customers Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDepositsFromCustomersExplanatory
361 1039 - Disclosure - Deposits by Banks Network

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364 Deposits by Banks Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDepositsFromBanksExplanatory
365 1040 - Disclosure - Repurchase Agreements - Non Trading Network

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368 Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfRepurchaseAgreementsNontradingExplanatory
369 1041 - Disclosure - Debt Securities in Issue Network

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372 Debt Securities in Issue Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDebtSecuritiesExplanatory
373 1042 - Disclosure - Subordinated Liabilities Network

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376 Subordinated Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSubordinatedLiabilitiesExplanatory
377 1043 - Disclosure - Provisions Network

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380 Provisions Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfProvisionsExplanatory
381 1044 - Disclosure - Retirement Benefit Plans Network

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384 Retirement Benefit Plans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEmployeeBenefitsExplanatory
385 1045 - Disclosure - Contingent Liabilities And Commitments Network

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388 Contingent Liabilities And Commitments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCommitmentsAndContingentLiabilitiesExplanatory
389 1046 - Disclosure - Share Capital Network

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392 Share Capital Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIssuedCapitalExplanatory
393 1047 - Disclosure - Other Equity Instruments Network

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395 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
396 Other Equity Instruments Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherEquityInstrumentsExplanatory
397 1048 - Disclosure - Non-Controlling Interests Network

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400 Non-Controlling Interests Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNoncontrollingInterestsExplanatory
401 1049 - Disclosure - Changes in Liabilities Arising from Financing Activities Network

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403 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
404 Changes in Liabilities Arising from Financing Activities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfReconciliationOfLiabilityArisingFromFinancingActivitiesExplanatory
405 1050 - Disclosure - Assets Charged As Security For Liabilities And Collateral Accepted As Security For Assets Network

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408 Assets Charged As Security For Liabilities And Collateral Accepted As Security For Assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCollateralExplanatory
409 1051 - Disclosure - Share-Based Compensation Network

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412 Share-Based Compensation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSharebasedPaymentArrangementsExplanatory
413 1052 - Disclosure - Transactions With Directors and Other Key Management Personnel Network

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416 Transactions With Directors and Other Key Management Personnel Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationAboutKeyManagementPersonnelExplanatory
417 1053 - Disclosure - Related Party Disclosures Network

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420 Related Party Disclosures Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRelatedPartyExplanatory
421 1054 - Disclosure - Financial Instruments Network

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423 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
424 Financial Instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsExplanatory
425 1055 - Disclosure - Offsetting Financial Assets and Liabilities Network

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428 Offsetting Financial Assets and Liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOffsettingOfFinancialAssetsAndFinancialLiabilitiesExplanatory
429 1056 - Disclosure - Ring-Fencing Network

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432 Ring-Fencing Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfRingFencingExplanatory
433 1057 - Disclosure - Transition to IFRS 9 Network

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436 Transition to IFRS 9 Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfImpactOfAdoptionOfIFRS9Explanatory
437 1058 - Disclosure - Events After the Balance Sheet Date Network

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440 Events After the Balance Sheet Date Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEventsAfterReportingPeriodExplanatory
441 1059 - Disclosure - Accounting Policies (Policies) Network

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444 Basis of preparation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBasisOfPreparationOfFinancialStatementsExplanatory
445 Consolidation Concept (Text Block (HTML)) For Period ck0001087711:DescriptionOfAccountingPolicyForConsolidationTextBlock
446 Foreign currency translation Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForForeignCurrencyTranslationExplanatory
447 Revenue recognition Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForRecognitionOfRevenue
448 Borrowing costs Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForBorrowingCostsExplanatory
449 Pensions and other post-retirement benefits Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForEmployeeBenefitsExplanatory
450 Share-based payments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForSharebasedPaymentTransactionsExplanatory
451 Goodwill and other intangible assets Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIntangibleAssetsAndGoodwillExplanatory
452 Property, plant and equipment Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForPropertyPlantAndEquipmentExplanatory
453 Financial instruments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForFinancialInstrumentsExplanatory
454 Derivative financial instruments Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForDerivativeFinancialInstrumentsExplanatory
455 Offsetting financial assets and liabilities Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForOffsettingOfFinancialInstrumentsExplanatory
456 Hedge accounting Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForHedgingExplanatory
457 Securitisation transactions Concept (Text Block (HTML)) For Period ck0001087711:DescriptionOfAccountingPolicyForSecuritisationTransactionsExplanatory
458 Impairment of non-financial assets Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForImpairmentOfNonfinancialAssetsExplanatory
459 Leases Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForLeasesExplanatory
460 Income taxes, including deferred taxes Concept (Text Block (HTML)) For Period ck0001087711:DescriptionOfAccountingPolicyForIncomeTaxAndDeferredIncomeTaxExplanatory
461 Cash and cash equivalents Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyToDetermineComponentsOfCashAndCashEquivalents
462 Provisions Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForProvisionsExplanatory
463 Share capital Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIssuedCapitalExplanatory
464 Accounting policies relating to comparatives - IAS 39: Financial Instruments: Recognition and Measurement Concept (Text Block (HTML)) For Period ck0001087711:DescriptionOfAccountingPolicyForFinancialInstrumentsRecognitionAndMeasurementExplanatory
465 Critical Judgements and Accounting Estimates Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAccountingJudgementsAndEstimatesExplanatory
466 1060 - Disclosure - Credit risk (Tables) Network

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469 Segments [member] Member ifrs-full:SegmentsMember
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476 Statement [LineItems] LineItems ck0001087711:StatementLineItems
477 Summary of Exposures to Credit Risk in Business Segments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfCreditRiskExposureExplanatory
478 Types Of Customers And HowTo Manage Them Concept (Text Block (HTML)) For Period ck0001087711:TypesOfCustomersAndHowToManageThemExplanatory
479 Summary of Key Metrics to Measure and Control Credit Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfKeyCreditRiskMetricsExplanatoryExplanatory
480 Summary of Annual Growth Rates Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfAnnualGrowthRatesForecastExplanatory
481 Summary of Probability Weightings Applied to Scenarios Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfProbabilityWeightingsOfScenariosExplanatory
482 Summary of Quantitative Criteria to Measure Significant Increase in Credit Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfQuantitativeCriteriaToMeasureSignificantIncreaseInCreditRiskExplanatory
483 Summary of Qualitative Criteria to Measure Significant Increase in Credit Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfQualitativeCriteriaToMeasureSignificantIncreaseInCreditRiskExplanatory
484 Summary of Difference Between Maximum and Net Exposure to Credit Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDifferenceBetweenMaximumAndNetExposureToCreditRiskExplanatory
485 Summary of Difference Between Maximum and Net Exposure to Credit Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDifferenceBetweenMaximumAndNetExposureToCreditRiskOnAssetsMeasuredAtFVTPLExplanatory
486 Summary of Credit Rating of Financial Assets Subject to Credit Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCreditRatingOfFinancialAssetsSubjectToCreditRiskExplanatory
487 Summary of Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCreditPerformanceExplanatory
488 Summary of IFRS 9 Credit Quality Concept (Text Block (HTML)) For Period ck0001087711:SummaryOfIFRS9CreditQualityExplanatory
489 Summary of Stage 2 Decomposition Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfStageTwoDecompositionExplanatory
490 Summary of Reconciliation of Exposures, ECL and Net Carrying Amounts Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfReconciliationOfExposuresECLAndNetCarryingAmountsExplanatory
491 Summary of ECL Reconciliation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsExplanatory
492 Summary of Country Risk Explosures Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCountryRiskExposuresExplanatory
493 Summary of Balances with Other Banco Santander Companies Concept (Text Block (HTML)) For Period ck0001087711:DisclosuresOfBalancesWithOtherBancoSantanderEntitiesExplanatory
494 Summary of Types of Credit Risk Mitigation Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfTypesOfCreditRiskMitigationExplanatory
495 Summary of Residential Mortgages by Borrower Profile Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgageLoansByBorrowerProfileExplanatory
496 Summary of Residential Mortgages by Interest Rate Profile Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesByInterestRateProfileExplanatory
497 Summary of Residential Mortgages by Geographical Distribution Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgageLoansByGeographicalDistributionExplanatory
498 Summary of Residential Mortgages by Average Loan Size for New Business Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesByAverageLoanSizeForNewBusinessExplanatory
499 Summary of Residential Mortgages by Loan Size Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgageLoansByLoanSizeExplanatory
500 Summary of Residential Mortgages by Loan to Value Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesByLoanToValueExplanatory
501 Summary of Residential Mortgages by Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesbyCreditPerformanceExplanatory
502 Summary of Modification of Loan Terms Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfModificationOfLoanTermsExplanatory
503 Summary of Residential Mortgages by Forbearance Applied Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesByForbearanceAppliedExplanatory
504 Summary of Residential Mortgages Portfolios of Particular Interest by Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesPortfoliosOfParticularInterestByCreditPerformanceExplanatory
505 Summary of Residential Mortgages Portfolios of Particular Interest by Forbearance Applied Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfResidentialMortgagesPortfoliosOfParticularInterestByForbearanceAppliedExplanatory
506 Summary of Consumer (Auto) Finance and Other Unsecured Lending by Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfConsumerAutoFinanceAndOtherUnsecuredLendingByCreditPerformanceExplanatory
507 Summary of Consumer (Auto) Finance and Other Unsecured Lending By Forbearance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfConsumerAutoFinanceAndOtherUnsecuredLendingByForbearanceExplanatory
508 Summary of Business Banking by Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfBusinessBankingByCreditPerformanceExplanatoryTextBlock
509 Summary of Business Banking by Forbearance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfBusinessBankingByForbearanceExplanatoryTextBlock
510 Summary of Other Segments Exposures By Credit Rating Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherSegmentExposuresByCreditRatingExplanatory
511 Summary of Other Segments Exposures by Geographical Distribution Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherSegmentsExposuresByGeographicalDistributionExplanatory
512 Summary of Other Segments Exposures by Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherSegmentsExposuresByCreditPerformanceExplanatory
513 Summary of Other Segments by Forbearance Applied Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherSegmentByForbearanceAppliedExplanatory
514 Summary of Commercial Real Estate by Credit Performance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCommercialRealEstateByCreditPerformanceExplanatory
515 Summary of Commercial Real Estate by Loan to Value Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCommercialRealEstateByLoanToValueExplanatory
516 Summary of Commercial Real Estate by Sector Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCommercialRealEstateBySectorExplanatory
517 Social Housing Exposure Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfSocialHousingExposureExplanatory
518 1061 - Disclosure - Market risk (Tables) Network

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521 Summary of Balance Sheet Allocation by Market Risk Classification Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfBalanceSheetAllocationByMarketRiskClassificationExplanatory
522 Summary of NIM and EVE Sensitivity of Interest Rate Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfNimAndEveSensitivityOfInterestRateRiskExplanatory
523 Summary of Internal VaR for Exposure to Main Classes of Risk Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfInternalVarForExposureToMainClassesOfRiskExplanatory
524 1062 - Disclosure - Liquidity risk (Tables) Network

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527 Summary of Reconciliation of Wholesale Funding to Balance Sheet Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfReconciliationOfWholesaleFundingToBalanceSheetExplanatory
528 Summary of Sources of Wholesale Funding by Maturity Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfWholesaleFundingByMaturityExplanatory
529 Summary of Wholesale Funding by Currency Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCurrencyCompositionOfWholesaleFundingExplanatory
530 Summary of External Term Issuance (Sterling Equivalent) Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfTermIssuanceExplanatory
531 1063 - Disclosure - Capital risk (Tables) Network

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534 Summary of Regulatory Capital Resources Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfRegulatoryCapitalResourcesExplanatory
535 1064 - Disclosure - Accounting Policies (Tables) Network

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538 Schedule of Useful Lives or Depreciation Rates Used for Property, Plant and Equipment Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfUsefulLivesOrDepreciationRatesPropertyPlantAndEquipmentExplanatory
539 Summary of Probability Weights Applied for Each Scenario of Expected Credit Losses Allowance Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfBaseExpectedCreditLossesToProbabilityWeightedEstimatedCreditLossesExplanatory
540 1065 - Disclosure - Segments (Tables) Network

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542 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
543 Summary of Results by Segment Concept (Text Block (HTML)) For Period ck0001087711:SummaryOfResultsBySegmentExplanatory
544 1066 - Disclosure - Net Interest Income (Tables) Network

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547 Summary of Net Interest Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfNetInterestIncomeExplanatory
548 1067 - Disclosure - Net Fee and Commission Income (Tables) Network

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551 Summary of Net Fee and Commission Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfNetFeeAndCommissionIncomeExplanatory
552 1068 - Disclosure - Net Trading and Other Income (Tables) Network

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555 Summary of Net Trading and Other Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfNetTradingAndOtherIncomeExplanatory
556 1069 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges (Tables) Network

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559 Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOperatingExpensesBeforeImpairmentLossesProvisionsAndChargesExplanatory
560 Summary of Deferred Performance Awards Concept (Text Block (HTML)) For Period ck0001087711:DeferredPerformanceAwardsExplanatory
561 Summary of Amount of Bonus Awarded to Employees Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfAmountOfBonusAwardedToEmployeesExplanatory
562 1070 - Disclosure - Audit and Other Services (Tables) Network

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565 Summary of Audit and Other Services Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfAuditAndOtherServicesExplanatory
566 1071 - Disclosure - Credit Impairment Losses and Provisions (Tables) Network

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569 Summary of Impairment Losses and Provisions Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailedInformationOfImpairmentLossesAndProvisionsExplanatory
570 1072 - Disclosure - Taxation (Tables) Network

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571 Implied Table Table

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572 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
573 Disclosure of Tax on Profit Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIncomeTaxExplanatory
574 Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfReconciliationOfChargeResultingFromApplyingUkCorporationTaxRateExplanatory
575 Disclosure of Movements in Current Tax Assets and Liabilities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfMovementInCurrentTaxAssetsAndLiabilitiesExplanatory
576 Disclosure of Deferred Tax Assets and Liabilities Including Movement in Deferred Tax Account Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDeferredTaxesExplanatory
577 1073 - Disclosure - Dividends on Ordinary Shares (Tables) Network

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580 Disclosure of Dividends on Ordinary Shares Declared and Paid Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDividendPerOrdinaryShareExplanatory
581 1074 - Disclosure - Trading Assets (Tables) Network

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583 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
584 Disclosure of Trading Assets Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfTradingAssetsExplanatory
585 1075 - Disclosure - Derivative Financial Instruments (Tables) Network

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588 Notional Amounts and Fair Values of Derivatives Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfNotionalAndFairValueAmountsOfDerivativeFinancialInstrumentsExplanatory
589 Analysis of the Notional and Fair Values of Derivatives by Trading and Settlement Method Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfAnalysisOfTheNotionalAndFairValuesOfDerivativesByTradingAndSettlementMethodExplanatory
590 Summary of Fixed Rate Hedged Instruments Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfFixedRateInstrumentsHedgedExplanatory
591 Summary of Possible Sources of Hedge ineffectiveness Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfPossibleSourcesOfHedgeInEffectivenessExplanatory
592 Summary of Maturity Profile and Average Price/Rate of Hedging Instruments Used in Hedging Strategies Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfMaturityProfileAndAveragePriceRateOfHedgingInstrumentsUsedInHedgingStrategiesExplanatory
593 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
594 Summary of Information About Hedging Ineffectiveness by Risk Category Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfInformationAboutHedgingIneffectivenessByRiskCategoryExplanatory
595 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 ck0001087711:DisclosureOfReconciliationByRiskCategoryOfComponentsOfEquityAndAnalysisOfOtherComprehensiveIncomeItemsResultingFromHedgeAccountingExplanatory
596 Summary of Details of Hedged Exposures by Hedging Strategies Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailsOfHedgedExposuresByHedgingStrategiesExplanatory
597 1076 - Disclosure - Other Financial Assets At Fair Value Through Profit Or Loss (Tables) Network

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600 Summary of Other Financial Assets at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsDesignatedAtFairValueThroughProfitOrLossExplanatory
601 1077 - Disclosure - Loans and Advances to Customers (Tables) Network

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604 Summary of Net Loans and Advances to Customers Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfNetLoansAndAdvancesToCustomersExplanatory
605 Summary of Movement in Impairment Loss Allowances Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfMovementInImpairmentLossAllowancesOnLoansAndAdvancesToCustomersExplanatory
606 Summary of Finance Lease and Hire Purchase Contract Receivables Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfFinanceLeaseAndHirePurchaseContractReceivablesExplanatory
607 1078 - Disclosure - Securitisations and Covered Bonds (Tables) Network

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609 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
610 Analysis of Securitisations and Covered Bonds Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfAnalysisOfSecuritisationsAndCoveredBondsExplanatory
611 Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfIssuancesAndRedemptionsOfSecuritisationAndCoveredBondProgrammesExplanatory
612 1079 - Disclosure - Transfers of Financial Assets Not Qualifying for Derecognition (Tables) Network

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613 Implied Table Table

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615 Carrying Amount of Financial Assets that Did Not Qualify for Derecognition and their Associated Financial Liabilities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfCarryingAmountOfFinancialAssetsThatDidNotQualifyForDerecognitionAndTheirAssociatedFinancialLiabilitiesExplanatory
616 1080 - Disclosure - Reverse Repurchase Agreements - Non Trading (Tables) Network

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617 Statement [table] Table

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618 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
619 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
620 Reverse repurchase agreements - non-trading [member] Member ck0001087711:ReverseRepurchaseAgreementsNontradingMember
621 Statement [LineItems] LineItems ck0001087711:StatementLineItems
622 Summary of Reverse Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRepurchaseAndReverseRepurchaseAgreementsExplanatory
623 1081 - Disclosure - Other Financial Assets At Amortised Cost (Tables) Network

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626 Summary of Other Financial Assets at Amortised Cost Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailedInformationOfOtherFinancialAssetsAtAmortisedCostExplanatory
627 1082 - Disclosure - Financial Assets At Fair Value Through Other Comprehensive Income (Tables) Network

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630 Summary of Financial Assets at Fair Value Through Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailedInformationAboutFinancialAssetsAtFairValueThroughOtherComprehensiveIncomeExplanatory
631 1083 - Disclosure - Financial Investments (Tables) Network

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633 Text block [abstract] Abstract ck0001087711:TextBlockAbstract
634 Summary of Financial Investments Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfSummaryOfFinancialInvestmentsExplanatory
635 1084 - Disclosure - Interests in Other Entities (Tables) Network

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636 Implied Table Table

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637 Investments accounted for using equity method [abstract] Abstract ifrs-full:InvestmentsAccountedForUsingEquityMethodAbstract
638 Schedule of Interests in Other Entities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailedInformationAboutInterestsInOtherEntitiesExplanatory
639 Schedule of Subsidiaries With Significant Non-Controlling Interests Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfSubsidiaryWithSignificantNonControllingInterestsExplanatory
640 1085 - Disclosure - Intangible Assets (Tables) Network

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643 Schedule of Goodwill Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGoodwillExplanatory
644 Schedule of Goodwill for Cash Generating Units Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesExplanatory
645 Schedule of Other Intangibles Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIntangibleAssetsExplanatory
646 1086 - Disclosure - Trading Liabilities (Tables) Network

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649 Schedule of Trading Liabilities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfTradingLiabilitiesExplanatory
650 1087 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss (Tables) Network

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653 Summary of Other Financial Liabilities at Fair Value Through Profit or Loss Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitsOrLossExplanatory
654 1088 - Disclosure - Deposits by Customers (Tables) Network

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657 Schedule of Deposits by Customers Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailedInformationAboutDepositsFromCustomersExplanatory
658 1089 - Disclosure - Deposits by Banks (Tables) Network

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661 Schedule of Deposits by Banks Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDepositsByBankExplanatory
662 1090 - Disclosure - Repurchase Agreements - Non Trading (Tables) Network

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665 Summary of Repurchase Agreements - Non Trading Concept (Text Block (HTML)) For Period ck0001087711:DetailedDisclosureOfRepurchaseAgreementsNontradingExplanatory
666 1091 - Disclosure - Debt Securities in Issue (Tables) Network

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669 Summary of Debt Securities in Issue Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDebtSecuritiesInIssueExplanatory
670 1092 - Disclosure - Subordinated Liabilities (Tables) Network

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673 Schedule of Subordinated Liabilities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDetailsOfSubordinatedLiabilitiesExplanatory
674 Summary of Undated Subordinated Liabilities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfUndatedSubordinatedLiabilitiesExplanatory
675 Summary of Dated Subordinated Liabilities Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfDatedSubordinatedLiabilitiesExplanatory
676 1093 - Disclosure - Provisions (Tables) Network

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679 Summary of Provisions Reconciliation Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfProvisionsReconciliationByClassExplanatory
680 Summary of Key Drivers of PPI Provision Balance and Forecast Assumptions Used in Calculating Provision Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfKeyDriversOfPPIProvisionBalanceAndForecastAssumptionsUsedInCalculatingProvisionExplanatory
681 1094 - Disclosure - Retirement Benefit Plans (Tables) Network

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684 Summary of Retirement Benefit Plans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDefinedBenefitPlansExplanatory
685 Summary of Pension Remeasurement (Gains)/Losses Recognised In Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfPensionRemeasurementsIncludedInOtherComprehensiveIncomeExplanatory
686 Total defined benefit plan amount charged to the income statement Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfTotalDefinedBenefitPlanAmountChargedToTheIncomeStatementExplanatory
687 Summary of Amounts Recognised in Other Comprehensive Income Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfAmountsRecognisedInOtherComprehensiveIncomeExplanatory
688 Disclosure of Movements in Present Value of Defined Benefit Obligations Concept (Text Block (HTML)) For Period ck0001087711:DisclosureOfMovementsInThePresentValueOfDefinedBenefitObligationsExplanatory
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943 Stage 1 [member] Member ck0001087711:StageOneMember
944 Stage 2 [member] Member ck0001087711:StageTwoMember
945 Stage 3 [member] Member ck0001087711:StageThreeMember
946 Loans and receivables securities [member] Member ifrs-full:LoansAndReceivablesCategoryMember
947 Available-for-sale [member] Member ifrs-full:FinancialAssetsAvailableforsaleCategoryMember
948 Held-to-maturity debt securities [member] Member ifrs-full:HeldtomaturityInvestmentsCategoryMember
949 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
950 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
951 Balance sheet exposures [member] Member ck0001087711:BalanceSheetExposuresMember
952 Off-Balance Sheet [member] Member ck0001087711:OffBalanceSheetMember
953 Advances secured on residential property [member] Member ck0001087711:AdvancesSecuredOnResidentialPropertyMember
954 Corporate loans [member] Member ifrs-full:CorporateLoansMember
955 Finance leases [member] Member ifrs-full:LeaseReceivablesMember
956 Other unsecured advances [member] Member ck0001087711:OtherUnsecuredLoansMember
957 Amounts due from fellow banco santander group subsidiaries and joint ventures [member] Member ck0001087711:AmountsDueFromSubsidiariesAndJointVenturesMember
958 Internal credit grades [axis] Axis ifrs-full:InternalCreditGradesAxis
959 Entity's total for internal credit grades [member] Member ifrs-full:EntitysTotalForInternalCreditGradesMember
960 Internal grade 9 [member] Member ck0001087711:InternalGradeNineMember
961 Internal grade 8 [member] Member ck0001087711:InternalGradeEightMember
962 Internal grade 7 [member] Member ck0001087711:InternalGradeSevenMember
963 Internal grade 6 [member] Member ck0001087711:InternalGradeSixMember
964 Internal grade 5 [member] Member ck0001087711:InternalGradeFiveMember
965 Internal grade 4 [member] Member ck0001087711:InternalGradeFourMember
966 Internal grade 3 to 1 [member] Member ck0001087711:InternalGradeThreeToOneMember
967 Other [member] Member ck0001087711:OtherInternalGradeMember
968 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
969 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
970 Cash and balances at central banks [member] Member ck0001087711:CashAndBalancesAtCentralBanksMember
971 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
972 Loans and advances to banks [member] Member ck0001087711:LoansAndAdvancesToBanksCategoryMember
973 Reverse repurchase agreements - non-trading [member] Member ck0001087711:ReverseRepurchaseAgreementsNontradingMember
974 Other financial assets at amortised cost [member] Member ck0001087711:OtherFinancialAssetsAtAmortisedCostMember
975 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
976 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
977 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
978 Assets [member] Member ifrs-full:ClassesOfAssetsMember
979 Financial assets at amortised cost [member] Member ifrs-full:FinancialAssetsAtAmortisedCostMember
980 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
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982 Credit risk [member] Member ifrs-full:CreditRiskMember
983 Disclosure of internal credit grades [line items] LineItems ifrs-full:DisclosureOfInternalCreditExposuresLineItems
984 Loss allowance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
985 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
986 1118 - Disclosure - Credit Risk - Summary of Credit Performance (Detail) Network

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987 Disclosure of credit risk exposure [table] Table

*

*

ifrs-full:DisclosureOfCreditRiskExposureTable
988 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
989 Products and services [member] Member ifrs-full:ProductsAndServicesMember
990 Mortgages [member] Member ifrs-full:MortgagesMember
991 Corporate loans [member] Member ifrs-full:CorporateLoansMember
992 Segments [axis] Axis ifrs-full:SegmentsAxis
993 Segments [member] Member ifrs-full:SegmentsMember
994 Retail banking [member] Member ck0001087711:RetailBankingMember
995 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
996 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
997 Corporate centre [member] Member ck0001087711:CorporateCentreMember
998 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
999 Assets [member] Member ifrs-full:ClassesOfAssetsMember
1000 Loans to Customers [member] Member ck0001087711:LoansToCustomersMember
1001 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1002 Customer loans Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1003 NPLs Concept (Monetary) As Of Debit ck0001087711:NonPerformingLoans
1004 NPL ratio Concept (Percent) As Of ck0001087711:RatioOfNonPerformingLoans
1005 Gross write-offs Concept (Monetary) For Period Debit ck0001087711:GrossWriteoffs
1006 Loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1007 1119 - Disclosure - Credit Risk - Summary of IFRS 9 Credit Quality (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfIFRS9CreditQuality
1008 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1009 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1010 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1011 Stage 1 [member] Member ck0001087711:StageOneMember
1012 Stage 2 [member] Member ck0001087711:StageTwoMember
1013 Stage 3 [member] Member ck0001087711:StageThreeMember
1014 Credit risk exposure approach [axis] Axis ck0001087711:CreditRiskExposureApproachAxis
1015 Credit risk exposure approach [member] Member ck0001087711:CreditRiskExposureApproachMember
1016 Drawn exposures [member] Member ck0001087711:DrawnExposuresMember
1017 Off-Balance Sheet Exposures [member] Member ck0001087711:OffbalanceSheetExposuresMember
1018 Segments [axis] Axis ifrs-full:SegmentsAxis
1019 Segments [member] Member ifrs-full:SegmentsMember
1020 Retail banking [member] Member ck0001087711:RetailBankingMember
1021 Retail banking mortgages [member] Member ck0001087711:RetailBankingMortgagesMember
1022 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1023 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1024 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1025 Stage Two Decomposition [axis] Axis ck0001087711:StageTwoDecompositionAxis
1026 Stage Two Decomposition [member] Member ck0001087711:StageTwoDecompositionMember
1027 Stage two below or equal to thirty DPD [member] Member ck0001087711:StageTwoBelowOrEqualToThirtyDpdMember
1028 Stage 2, above 30 DPD [member] Member ck0001087711:StageTwoAboveThirtyDPDMember
1029 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1030 Total exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1031 Loss Impairment: On Balance Sheet ECL Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1032 Loss Impairment: Off Balance Sheet ECL Concept (Monetary) As Of Credit ifrs-full:Provisions
1033 Total ECL Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1034 Total coverage ratio Concept (Percent) As Of ck0001087711:CoverageRatio
1035 1120 - Disclosure - Credit Risk - Summary of IFRS 9 Credit Quality (Parenthetical) (Detail) Network

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1036 Implied Table Table

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*

implied:Table
1037 Disclosure of credit risk exposure [abstract] Abstract ifrs-full:DisclosureOfCreditRiskExposureAbstract
1038 Average PD percentage Concept (Percent) For Period ck0001087711:AssetsInDefaultProbabilityOfDefault
1039 Retail mortgage offers in pipeline Concept (Monetary) For Period Debit ck0001087711:RetailMortgageOffersInPipeline
1040 1121 - Disclosure - Credit Risk - Summary of Stage 2 Decomposition (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfStage2Decomposition
1041 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1042 Stage Two Decomposition [axis] Axis ck0001087711:StageTwoDecompositionAxis
1043 Stage Two Decomposition [member] Member ck0001087711:StageTwoDecompositionMember
1044 Currently in Arrears [member] Member ck0001087711:StageTwoBelowThirtyDpdMember
1045 Deterioation in probability of default [member] Member ck0001087711:DeterioationInProbabilityOfDefaultMember
1046 Other [member] Member ck0001087711:OtherMember
1047 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1048 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1049 Stage 2 [member] Member ck0001087711:StageTwoMember
1050 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1051 Exposure Concept (Monetary) As Of ifrs-full:CreditExposure
1052 1122 - Disclosure - Credit Risk - Summary of Reconciliation of Exposures, ECL and Net Carrying Amounts (Detail) Network

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1053 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1054 Segments [axis] Axis ifrs-full:SegmentsAxis
1055 Segments [member] Member ifrs-full:SegmentsMember
1056 Retail banking [member] Member ck0001087711:RetailBankingMember
1057 Mortgages [member] Member ifrs-full:MortgagesMember
1058 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1059 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1060 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1061 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1062 Risks [member] Member ifrs-full:TypesOfRisksMember
1063 Drawn exposures [member] Member ck0001087711:DrawnExposuresMember
1064 Off-Balance Sheet Exposures [member] Member ck0001087711:OffbalanceSheetExposuresMember
1065 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1066 Total exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1067 Total ECL on drawn exposures Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1068 Total ECL on off-balance sheet exposures Concept (Monetary) As Of Credit ifrs-full:Provisions
1069 On-balance sheet net carrying amount Concept (Monetary) As Of Debit ck0001087711:NetCreditExposure
1070 Other items Concept (Monetary) For Period Debit ck0001087711:OtherReconcilingItems
1071 Adjusted net carrying amount Concept (Monetary) For Period Debit ck0001087711:AdjustedNetCarryingAmount
1072 Assets classified at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
1073 Non-financial assets Concept (Monetary) As Of Debit ck0001087711:NonFinancialAssets
1074 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
1075 1123 - Disclosure - Credit Risk - Summary of ECL Reconciliation (Detail) Network

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1076 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

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*

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1077 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
1078 Credit impairment of financial instruments [member] Member ifrs-full:CreditImpairmentOfFinancialInstrumentsMember
1079 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1080 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1081 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1082 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1083 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1084 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1085 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
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1087 Stage 1 [member] Member ck0001087711:StageOneMember
1088 Stage 2 [member] Member ck0001087711:StageTwoMember
1089 Stage 3 [member] Member ck0001087711:StageThreeMember
1090 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1091 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1092 Stage 1 ECL [member] Member ck0001087711:StageOneExpectedCreditLossMember
1093 Stage 2 ECL [member] Member ck0001087711:StageTwoExpectedCreditLossMember
1094 Stage 3 ECL [member] Member ck0001087711:StageThreeExpectedCreditLossMember
1095 Total exposure [member] Member ck0001087711:TotalExposureMember
1096 Expected credit loss [member] Member ck0001087711:ExpectedCreditLossMember
1097 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
1098 Beginning balance Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1099 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1100 Change in economic scenarios Concept (Monetary) For Period Debit ck0001087711:IncreaseDecreaseThroughChangesInEconomicInputs
1101 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1102 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1103 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1104 Transfer to 12-month ECL Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1105 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1106 Transfer of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1107 Net re-measurement of ECL arising from transfer of stage Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1108 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1109 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1110 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1111 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1112 Ending balance Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1113 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1114 Net movement in the year Concept (Monetary) As Of ck0001087711:IncreaseDecreaseInTotalExpectedCreditLosses
1115 Net movement in the year Concept (Monetary) For Period Debit ck0001087711:IncreaseDecreaseInTotalFinancialAssets
1116 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ck0001087711:GrossImpairmentLossIncomeStatementCharge
1117 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001087711:FinancialAssetsPostWriteoffRecoveries
1118 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1119 1124 - Disclosure - Credit Risk - Summary of Country Risk Exposure (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfCountryRiskExposure
1120 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1121 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1122 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1123 Eurozone Countries [member] Member ifrs-full:CountryOfDomicileMember
1124 All Other Countries [member] Member ifrs-full:ForeignCountriesMember
1125 All Countries Excluding Eurozone Countries [member] Member ck0001087711:AllCountriesExcludingEurozoneCountriesMember
1126 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
1127 Counterparties [member] Member ifrs-full:CounterpartiesMember
1128 Governments [member] Member ifrs-full:GovernmentMember
1129 Government Guaranteed [member] Member ck0001087711:GovernmentGuaranteedMember
1130 Banks [member] Member ck0001087711:BankMember
1131 Other Financial Institutions [member] Member ck0001087711:OtherFinancialInstitutionsMember
1132 Retail [member] Member ck0001087711:RetailMember
1133 Corporate counterparty [member] Member ck0001087711:CorporateCounterpartyMember
1134 Geographical [Axis] Axis srt:StatementGeographicalAxis
1135 Geographical [Domain] Member srt:SegmentGeographicalDomain
1136 Ireland [member] Member country:IE
1137 Italy [member] Member country:IT
1138 Spain (excl. Banco Santander) [member] Member country:ES
1139 Portugal [member] Member country:PT
1140 France [member] Member country:FR
1141 Germany [member] Member country:DE
1142 Luxembourg [member] Member country:LU
1143 Other [member] Member ck0001087711:OtherCountriesMember
1144 UK [member] Member country:GB
1145 US [member] Member country:US
1146 Japan [member] Member country:JP
1147 Switzerland [member] Member country:CH
1148 Denmark [member] Member country:DK
1149 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1150 Risk exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1151 1125 - Disclosure - Credit Risk - Summary of Country Risk Exposure (Parenthetical) (Detail) Network

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1152 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1153 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1154 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1155 Eurozone Countries [member] Member ck0001087711:EuroZoneCountriesMember
1156 Geographical [Axis] Axis srt:StatementGeographicalAxis
1157 Geographical [Domain] Member srt:SegmentGeographicalDomain
1158 Netherlands [member] Member country:NL
1159 Belgium [Member] Member country:BE
1160 Greece [member] Member country:GR
1161 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1162 Risk exposures Concept (Monetary) As Of ifrs-full:CreditExposure
1163 1126 - Disclosure - Credit Risk - Summary of Balances with Other Banco Santander Companies (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfBalancesWithOtherBancoSantanderCompanies
1164 Disclosure of detailed information about financial instruments [table] Table

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*

ifrs-full:DisclosureOfFinancialInstrumentsTable
1165 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
1166 Counterparties [member] Member ifrs-full:CounterpartiesMember
1167 Banks [member] Member ck0001087711:BankMember
1168 Other Financial Institutions [member] Member ck0001087711:OtherFinancialInstitutionsMember
1169 Corporate counterparty [member] Member ck0001087711:CorporateCounterpartyMember
1170 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1171 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1172 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
1173 Geographical [Axis] Axis srt:StatementGeographicalAxis
1174 Geographical [Domain] Member srt:SegmentGeographicalDomain
1175 Spain (excl. Banco Santander) [member] Member country:ES
1176 UK [member] Member country:GB
1177 Uruguay [member] Member country:UY
1178 Other [member] Member ck0001087711:OtherCountriesMember
1179 Disclosure of detailed information about financial instruments [line items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
1180 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1181 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
1182 1127 - Disclosure - Credit Risk - Summary of Balances with Other Banco Santander Companies (Parenthetical) (Detail) Network

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1183 Disclosure of detailed information about financial instruments [table] Table

*

*

ifrs-full:DisclosureOfFinancialInstrumentsTable
1184 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1185 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1186 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
1187 Range [axis] Axis ifrs-full:RangeAxis
1188 Ranges [member] Member ifrs-full:RangesMember
1189 Top of Range [member] Member ifrs-full:TopOfRangeMember
1190 Disclosure of detailed information about financial instruments [line items] LineItems ifrs-full:DisclosureOfFinancialInstrumentsLineItems
1191 Financial liabilities allocated to other countries Concept (Monetary) For Period Credit ck0001087711:FinancialLiabilitiesAllocatedToOtherCountries
1192 1128 - Disclosure - Credit Risk - Summary of Types of Credit Risk Mitigation (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfTypesOfCreditRiskMitigation
1193 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
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1195 Segments [member] Member ifrs-full:SegmentsMember
1196 Residential mortgages [member] Member ck0001087711:ResidentialMortgagesMember
1197 Business Banking [member] Member ck0001087711:BusinessBankingMember
1198 Consumer (auto) finance [member] Member ck0001087711:ConsumerFinanceMember
1199 Unsecured Lending [member] Member ck0001087711:UnsecuredLendingMember
1200 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1201 Types of credit risk mitigation, including collateral, across portfolios Concept (Text/String) For Period ck0001087711:CreditRiskMitigationDescription
1202 1129 - Disclosure - Credit Risk - Summary of ECL Reconciliation for Retail Segment (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfECLReconciliationForRetailSegment
1203 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

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ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
1204 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
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1206 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1207 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1208 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1209 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1210 Stage 1 ECL [member] Member ck0001087711:StageOneExpectedCreditLossMember
1211 Stage 2 ECL [member] Member ck0001087711:StageTwoExpectedCreditLossMember
1212 Stage 3 ECL [member] Member ck0001087711:StageThreeExpectedCreditLossMember
1213 Total exposure [member] Member ck0001087711:TotalExposureMember
1214 Expected credit loss [member] Member ck0001087711:ExpectedCreditLossMember
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1217 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1218 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1219 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
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1222 Stage 2 [member] Member ck0001087711:StageTwoMember
1223 Stage 3 [member] Member ck0001087711:StageThreeMember
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1226 Retail banking [member] Member ck0001087711:RetailBankingMember
1227 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
1228 Beginning balance Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1229 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1230 Change in economic scenarios Concept (Monetary) For Period Debit ck0001087711:IncreaseDecreaseThroughChangesInEconomicInputs
1231 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1232 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1233 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1234 Transfer to 12-monthECL Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1235 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1236 Transfers of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1237 Net remeasurement of ECL on stage transfer Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1238 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1239 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1240 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1241 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1242 Ending balance Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1243 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1244 Net movement in the year Concept (Monetary) As Of ck0001087711:IncreaseDecreaseInTotalExpectedCreditLosses
1245 Net movement in the year Concept (Monetary) For Period Debit ck0001087711:IncreaseDecreaseInTotalFinancialAssets
1246 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ck0001087711:GrossImpairmentLossIncomeStatementCharge
1247 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001087711:FinancialAssetsPostWriteoffRecoveries
1248 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1249 1130 - Disclosure - Credit Risk - Summary of Residential Mortgages by Borrower Profile (Detail) Network

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1250 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
1251 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1252 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1253 First-Time Buyers [member] Member ck0001087711:FirstTimeBuyersMember
1254 Home Movers [member] Member ck0001087711:HomeMoversMember
1255 Remortgagers [member] Member ck0001087711:RemortgagersMember
1256 Buy-To-Let [member] Member ck0001087711:BuyToLetMember
1257 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1258 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1259 Stock [member] Member ck0001087711:StockMember
1260 New Business [member] Member ck0001087711:NewBusinessMember
1261 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1262 Risks [member] Member ifrs-full:TypesOfRisksMember
1263 Credit risk [member] Member ifrs-full:CreditRiskMember
1264 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1265 Residential mortgage loans Concept (Monetary) As Of Debit ck0001087711:ResidentialMortgageLoans
1266 Percentage of residential mortgage loans Concept (Percent) As Of ck0001087711:ResidentialMortgageLoansPercentage
1267 1131 - Disclosure - Credit Risk - Additional Information (Detail) Network

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1268 Disclosure of internal credit grades [table] Table

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*

ifrs-full:DisclosureOfInternalCreditExposuresTable
1269 Range [axis] Axis ifrs-full:RangeAxis
1270 Ranges [member] Member ifrs-full:RangesMember
1271 Greater Than 2.0m [member] Member ck0001087711:RangeFiveMember
1272 Less Than 70% [member] Member ck0001087711:LessThanOrEqualToSeventyPercentageMember
1273 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1274 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1275 Internal Remortgages [member] Member ck0001087711:InternalRemortgagesMember
1276 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1277 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1278 Development Loans [member] Member ck0001087711:DevelopmentLoansMember
1279 Segments [axis] Axis ifrs-full:SegmentsAxis
1280 Segments [member] Member ifrs-full:SegmentsMember
1281 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1282 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstate1Member
1283 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1284 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1285 Mortgages [member] Member ifrs-full:MortgagesMember
1286 Pre Two Thousand Nine Loans [member] Member ck0001087711:PreTwoThousandNineLoansMember
1287 Corporate loans [member] Member ifrs-full:CorporateLoansMember
1288 Customer Loans [member] Member ck0001087711:CustomerLoansMember
1289 Legacy Portfolios in Run-Off [member] Member ck0001087711:LegacyPortfoliosInRunoffMember
1290 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1291 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1292 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1293 Non performing loans [member] Member ck0001087711:NonPerformingLoansMember
1294 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1295 Risks [member] Member ifrs-full:TypesOfRisksMember
1296 Credit risk [member] Member ifrs-full:CreditRiskMember
1297 Maturity [axis] Axis ifrs-full:MaturityAxis
1298 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
1299 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
1300 Disclosure of internal credit grades [line items] LineItems ifrs-full:DisclosureOfInternalCreditExposuresLineItems
1301 Internal remortgages Concept (Monetary) As Of Debit ck0001087711:ResidentialMortgageLoansNewBusiness
1302 Advances and flexible mortgage drawdowns Concept (Monetary) As Of Debit ck0001087711:AdvancesAndFlexibleMortgageDrawdowns
1303 Number of individual mortgage loans Concept (Integer) As Of ck0001087711:NumberOfResidentialMortgageLoans
1304 New business number of individual mortgage loans Concept (Integer) As Of ck0001087711:NumberOfResidentialMortgageLoansNewBusiness
1305 Parts of the loans in negative equity that were effectively uncollateralised Concept (Monetary) As Of Debit ck0001087711:UncollateralisedLoans
1306 Average consumer finance loan size Concept (Monetary) As Of Credit ck0001087711:AverageConsumerFinanceLoanSize
1307 Average unsecured loan Concept (Monetary) As Of Credit ck0001087711:AverageUnsecuredLoan
1308 Credit card balances Concept (Monetary) As Of Credit ck0001087711:CreditCardBalance
1309 Percenatage of reverse repos to exposure Concept (Percent) For Period ck0001087711:PercentageOfCollateralHeldForReverseReposToExposure
1310 Percentage of collateral held against impaired loans Concept (Percent) As Of ck0001087711:CollateralHeldAgainstImpairedLoansPercentage
1311 Collateral held against Credit impaired assets Concept (Monetary) As Of Debit ck0001087711:CollateralHeldAgainstLoanCreditimpairedAssets
1312 Credit impaired assets Concept (Monetary) As Of Debit ck0001087711:CreditimpairedAssets
1313 Number of clients Concept (Integer) As Of ck0001087711:NumberOfClients
1314 Rate of derivative exposure with client Concept (Percent) As Of ck0001087711:DerivativeExposureWithClientPercentage
1315 Weighted-average credit rating percent Concept (Percent) As Of ifrs-full:ExpectedCreditLossRate
1316 Cash collateral held against portfolio Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
1317 Loans written down Concept (Monetary) As Of Credit ck0001087711:LoansAndAdvancesToCustomersWrittenDown
1318 Loan percentage Concept (Percent) As Of ck0001087711:PercentageOfLendingToCorporates
1319 Loan percentage Concept (Percent) As Of ck0001087711:PercentageOfLendingToCustomers
1320 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1321 Percentage of loan to value Concept (Percent) As Of ck0001087711:PercentageOfLoanToValueStock
1322 Loan percentage Concept (Percent) For Period ck0001087711:PercentageOfLoansWithDevelopmentRiskInCommercialRealEstatePortfolio
1323 Average loan balance Concept (Monetary) For Period Credit ck0001087711:AverageLoans
1324 Loans and advances to customers with higher LTV ratio Concept (Monetary) As Of Debit ck0001087711:LoansAndAdvancesToCustomersWithHigherLoanToValueRatio
1325 Percentage of maximum acceptable LTV ratio Concept (Percent) For Period ck0001087711:PercentageOfAcceptableMaximumLoanToValueRatio
1326 Impairment loss allowance Concept (Monetary) As Of Debit ck0001087711:ImpairmentLossAllowances
1327 1132 - Disclosure - Credit Risk - Summary of Residential Mortgages by Interest Rate Profile (Detail) Network

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1328 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
1329 Types of interest rates [axis] Axis ifrs-full:TypesOfInterestRatesAxis
1330 Interest rate types [member] Member ifrs-full:InterestRateTypesMember
1331 Fixed Rate [member] Member ifrs-full:FixedInterestRateMember
1332 Variable Rate [member] Member ifrs-full:FloatingInterestRateMember
1333 Standard Variable Rate [member] Member ck0001087711:StandardVariableRateMember
1334 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1335 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1336 Stock [member] Member ck0001087711:StockMember
1337 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1338 Risks [member] Member ifrs-full:TypesOfRisksMember
1339 Credit risk [member] Member ifrs-full:CreditRiskMember
1340 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1341 Residential mortgage loans Concept (Monetary) As Of Debit ck0001087711:ResidentialMortgageLoans
1342 Percentage of residential mortgage loans Concept (Percent) As Of ck0001087711:ResidentialMortgageLoansPercentage
1343 1133 - Disclosure - Credit Risk - Summary of Residential Mortgages by Geographical Distribution (Detail) Network

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1344 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1345 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1346 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1347 London [member] Member ck0001087711:LondonMember
1348 Midlands and East Anglia [member] Member ck0001087711:MidlandsAndEastAngliaMember
1349 North UK [member] Member ck0001087711:NorthUKMember
1350 Northern Ireland [member] Member ck0001087711:NorthernIrelandMember
1351 Scotland [member] Member ck0001087711:ScotlandMember
1352 South East Excluding London [member] Member ck0001087711:SouthEastExcludingLondonMember
1353 South West and Wales and Other [member] Member ck0001087711:SouthWestAndWalesAndOtherMember
1354 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1355 Risks [member] Member ifrs-full:TypesOfRisksMember
1356 Credit risk [member] Member ifrs-full:CreditRiskMember
1357 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1358 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1359 Stock [member] Member ck0001087711:StockMember
1360 New Business [member] Member ck0001087711:NewBusinessMember
1361 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1362 Residential mortgage loans Concept (Monetary) As Of Debit ck0001087711:ResidentialMortgageLoans
1363 1134 - Disclosure - Credit Risk - Summary of Residential Mortgages by Average Loan Size for New Business (Detail) Network

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1364 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1365 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1366 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1367 South East Including London [member] Member ck0001087711:SouthEastIncludingLondonMember
1368 Rest of UK [member] Member ck0001087711:RestOfUKMember
1369 UK [member] Member country:GB
1370 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1371 New business residential mortgage loans average size Concept (Monetary) As Of Debit ck0001087711:ResidentialMortgageLoansNewBusinessAverageSize
1372 1135 - Disclosure - Credit Risk - Summary of Residential Mortgages by Loan Size (Detail) Network

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1373 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1374 Range [axis] Axis ifrs-full:RangeAxis
1375 Ranges [member] Member ifrs-full:RangesMember
1376 Less Than 0.25m [member] Member ck0001087711:RangeOneMember
1377 0.25m-0.50m[member] Member ck0001087711:RangeTwoMember
1378 0.50m-1.0m [member] Member ck0001087711:RangeThreeMember
1379 1.0m-2.0m [member] Member ck0001087711:RangeFourMember
1380 Greater Than 2.0m [member] Member ck0001087711:RangeFiveMember
1381 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1382 Risks [member] Member ifrs-full:TypesOfRisksMember
1383 Credit risk [member] Member ifrs-full:CreditRiskMember
1384 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
1385 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
1386 South East Including London [member] Member ck0001087711:SouthEastIncludingLondonMember
1387 UK [member] Member country:GB
1388 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1389 Residential mortgage loans Concept (Monetary) As Of Debit ck0001087711:ResidentialMortgageLoans
1390 1136 - Disclosure - Credit Risk - Summary of Residential Mortgages by Loan to Value (Detail) Network

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1391 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1392 Range [axis] Axis ifrs-full:RangeAxis
1393 Ranges [member] Member ifrs-full:RangesMember
1394 Up to 50% [member] Member ck0001087711:UpToFiftyPercentageMember
1395 50 - 75% [member] Member ck0001087711:FiftyToSeventyFivePercentageMember
1396 75 - 85% [member] Member ck0001087711:SeventyFiveToEightyFivePercentageMember
1397 85 - 100% [member] Member ck0001087711:EightyFiveToHundredPercentageMember
1398 Greater Than 100% [member] Member ck0001087711:GreaterThanHundredPercentageMember
1399 Simple Average [member] Member ck0001087711:SimpleAverageMember
1400 Valuation Weighted Average LTV [member] Member ck0001087711:ValuationWeightedAverageMember
1401 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1402 Risks [member] Member ifrs-full:TypesOfRisksMember
1403 Credit risk [member] Member ifrs-full:CreditRiskMember
1404 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1405 Percentage of loan to value, Stock Concept (Percent) As Of ck0001087711:PercentageOfLoanToValueResidentialMortgages
1406 Collateral value of residential properties, Stock Concept (Monetary) As Of Debit ck0001087711:CollateralValueOfResidentialProperties
1407 Percentage of loan to value, NPL stock Concept (Percent) As Of ck0001087711:PercentageOfLoanToValueResidentialMortgagesNPLStock
1408 Collateral value of residential properties, NPL stock Concept (Monetary) As Of Debit ck0001087711:CollateralValueOfResidentialPropertiesNPLStock
1409 Percentage of loan to value, New business Concept (Percent) As Of ck0001087711:PercentageOfLoanToValueResidentialMortgagesNewBusiness
1410 Collateral value of residential properties, New business Concept (Monetary) As Of Debit ck0001087711:CollateralValueOfResidentialPropertiesNewBusiness
1411 1137 - Disclosure - Credit Risk - Summary of Residential Mortgages by Loan to Value (Parenthetical) (Detail) Network

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1412 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1413 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1414 Risks [member] Member ifrs-full:TypesOfRisksMember
1415 Credit risk [member] Member ifrs-full:CreditRiskMember
1416 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1417 Collateral against loans in negative equity Concept (Monetary) As Of Debit ck0001087711:CollateralValueOfResidentialPropertiesInNegativeEquity
1418 1138 - Disclosure - Credit Risk - Summary of Residential Mortgages by Credit Performance (Detail) Network

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1419 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
1420 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1421 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1422 Performing Loans [member] Member ck0001087711:PerformingLoansMember
1423 Early Arrear Loans [member] Member ck0001087711:EarlyArrearLoansMember
1424 Non Performing Loans by Arrears [member] Member ck0001087711:NonPerformingLoansByArrearsMember
1425 Non Performing Loans by Bankruptcy [member] Member ck0001087711:NonPerformingLoansByBankruptcyMember
1426 Non Performing Loans by Maturity Default [member] Member ck0001087711:NonPerformingLoansByMaturityDefaultMember
1427 Non-performing loans by forbearance [member] Member ck0001087711:NonPerformingLoansByForbearanceMember
1428 Non Performing Loans by Properties in Possession [member] Member ck0001087711:NonPerformingLoansByPropertiesInPossessionMember
1429 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1430 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1431 Stage 1 [member] Member ck0001087711:StageOneMember
1432 Stage 2 [member] Member ck0001087711:StageTwoMember
1433 Stage 3 [member] Member ck0001087711:StageThreeMember
1434 Segments [axis] Axis ifrs-full:SegmentsAxis
1435 Segments [member] Member ifrs-full:SegmentsMember
1436 Mortgages [member] Member ifrs-full:MortgagesMember
1437 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1438 Risks [member] Member ifrs-full:TypesOfRisksMember
1439 Credit risk [member] Member ifrs-full:CreditRiskMember
1440 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1441 Past due status [member] Member ifrs-full:PastDueStatusMember
1442 Later Than 1 Month and Not Later Than 2 Months [member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1443 Later Than 2 Months And Not Later Than 3 Months [member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1444 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1445 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1446 Non performing loans Concept (Monetary) As Of Debit ck0001087711:NonPerformingLoans
1447 Impairment loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1448 Stage 2 ratio Concept (Percent) As Of ck0001087711:StageTwoRatio
1449 Stage 3 ratio Concept (Percent) As Of ck0001087711:StageThreeRatio
1450 Early arrears ratio Concept (Percent) As Of ck0001087711:LoansEarlyArrearsRatio
1451 NPL ratio Concept (Percent) As Of ck0001087711:RatioOfNonPerformingLoans
1452 1139 - Disclosure - Credit Risk - Summary of Residential Mortgages by Credit Performance (Parenthetical) (Detail) Network

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1453 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1454 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
1455 Past due status [member] Member ifrs-full:PastDueStatusMember
1456 Later Than 1 day and Not Later Than 1 Month [member] Member ck0001087711:LaterThanOneDayAndNotLaterThanOneMonthMember
1457 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1458 Non performing loans Concept (Monetary) As Of Debit ck0001087711:NonPerformingLoans
1459 1140 - Disclosure - Credit Risk - Summary of ECL Reconciliation (Residential Mortgages) (Detail) Network

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1460 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

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ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
1461 Segments [axis] Axis ifrs-full:SegmentsAxis
1462 Segments [member] Member ifrs-full:SegmentsMember
1463 Residential mortgages [member] Member ck0001087711:ResidentialMortgagesMember
1464 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1465 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1466 Stage 1 ECL [member] Member ck0001087711:StageOneExpectedCreditLossMember
1467 Stage 2 ECL [member] Member ck0001087711:StageTwoExpectedCreditLossMember
1468 Stage 3 ECL [member] Member ck0001087711:StageThreeExpectedCreditLossMember
1469 Total exposure [member] Member ck0001087711:TotalExposureMember
1470 Expected credit loss [member] Member ck0001087711:ExpectedCreditLossMember
1471 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1472 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1473 Stage 1 [member] Member ck0001087711:StageOneMember
1474 Stage 2 [member] Member ck0001087711:StageTwoMember
1475 Stage 3 [member] Member ck0001087711:StageThreeMember
1476 Type of measurement of expected credit losses [axis] Axis ifrs-full:TypeOfMeasurementOfExpectedCreditLossesAxis
1477 Type of measurement of expected credit losses [member] Member ifrs-full:TypeOfMeasurementOfExpectedCreditLossesMember
1478 Subject to 12-month ECL [member] Member ifrs-full:TwelvemonthExpectedCreditLossesMember
1479 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
1480 Credit impairment of financial instruments [axis] Axis ifrs-full:CreditImpairmentOfFinancialInstrumentsAxis
1481 Credit impairment of financial instruments [member] Member ifrs-full:CreditImpairmentOfFinancialInstrumentsMember
1482 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1483 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
1484 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
1485 Beginning balance Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1486 Beginning balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1487 Change in economic scenarios Concept (Monetary) For Period Debit ck0001087711:IncreaseDecreaseThroughChangesInEconomicInputs
1488 Changes to model Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughChangesInModelsOrRiskParametersFinancialAssets
1489 Transfer to lifetime ECL (not-credit impaired) Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToLifetimeEclNotCreditImpairedFinancialAssets
1490 Transfer to credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToCreditImpairedFinancialAssets
1491 Transfer to 12-monthECL Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersToTwelveMonthEclFinancialAssets
1492 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1493 Transfers of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
1494 Net remeasurement of ECL on stage transfer Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughNetRemeasurementOfECLOnStageTransfer
1495 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1496 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1497 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1498 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
1499 Ending balance Concept (Monetary) As Of Credit ck0001087711:TotalExpectedCreditLosses
1500 Ending balance Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
1501 Net movement in the year Concept (Monetary) As Of ck0001087711:IncreaseDecreaseInTotalExpectedCreditLosses
1502 Net movement in the year Concept (Monetary) For Period Debit ck0001087711:IncreaseDecreaseInTotalFinancialAssets
1503 Charge/(release) to the Income Statement Concept (Monetary) For Period Debit ck0001087711:GrossImpairmentLossIncomeStatementCharge
1504 Recoveries net of collection costs Concept (Monetary) For Period Debit ck0001087711:FinancialAssetsPostWriteoffRecoveries
1505 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1506 1141 - Disclosure - Credit Risk - Summary of Modification of Loan Terms (Residential Mortgages) (Detail) Network

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1507 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
1508 Segments [axis] Axis ifrs-full:SegmentsAxis
1509 Segments [member] Member ifrs-full:SegmentsMember
1510 Mortgages [member] Member ifrs-full:MortgagesMember
1511 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
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1514 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
1515 1142 - Disclosure - Credit Risk - Summary of Residential Mortgages by Forbearance Applied (Detail) Network

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1516 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1520 Stage 3 [member] Member ck0001087711:StageThreeMember
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1522 Performing [member] Member ck0001087711:PerformingForbearanceMember
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1528 Term extension Concept (Monetary) As Of Debit ck0001087711:LoansTermExtensionForbearance
1529 Interest-only Concept (Monetary) As Of Debit ck0001087711:LoansInterestOnlyForbearance
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1532 Loans capitalisation forbearance Percentage Concept (Percent) As Of ck0001087711:LoansCapitalisationForbearancePercentage
1533 Loans term extension forbearance percentage Concept (Percent) As Of ck0001087711:LoansTermExtensionForbearancePercentage
1534 Loans interest only forbearance percentage Concept (Percent) As Of ck0001087711:LoansInterestOnlyForbearancePercentage
1535 Loans forbearance percentage Concept (Percent) As Of ck0001087711:LoansForbearancePercentage
1536 1143 - Disclosure - Credit Risk - Summary of Residential Mortgages Portfolios of Particular Interest by Credit Performance (Detail) Network

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1537 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1549 Later Than 2 Months And Not Later Than 3 Months [member] Member ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
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1558 Flexible Interest Loan [member] Member ck0001087711:FlexibleInterestLoanMember
1559 Loan To Value Greater Than 100% Loan [member] Member ck0001087711:LoanToValueGreaterThanHundredPercentageLoanMember
1560 Buy To Let Loan [member] Member ck0001087711:BuyToLetLoanMember
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1567 PIPs Concept (Monetary) As Of Debit ck0001087711:NonPerformingLoansByPropertiesInPossession
1568 1144 - Disclosure - Credit Risk - Summary of Residential Mortgages Portfolios of Particular Interest by Credit Performance (Parenthetical) (Detail) Network

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1569 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1575 1145 - Disclosure - Credit Risk - Summary of Residential Mortgages Portfolios of Particular Interest by Forbearance Applied (Detail) Network

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1576 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1580 Flexible Interest Loan [member] Member ck0001087711:FlexibleInterestLoanMember
1581 Loan To Value Greater Than 100% Loan [member] Member ck0001087711:LoanToValueGreaterThanHundredPercentageLoanMember
1582 Buy To Let Loan [member] Member ck0001087711:BuyToLetLoanMember
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1592 1146 - Disclosure - Credit Risk - Summary of Consumer (Auto) Finance and Other Unsecured Lending by Credit Performance (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfConsumerAutoFinanceAndOtherUnsecuredLendingByCreditPerformance
1593 Disclosure of credit risk exposure [table] Table

*

*

ifrs-full:DisclosureOfCreditRiskExposureTable
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1596 Consumer (auto) finance [member] Member ifrs-full:ConsumerLoansMember
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1598 Credit Card [member] Member ck0001087711:CreditCardMember
1599 Overdrafts [member] Member ck0001087711:OverdraftsMember
1600 Other unsecured advances [member] Member ck0001087711:OtherUnsecuredLoansMember
1601 Segments [axis] Axis ifrs-full:SegmentsAxis
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1620 1147 - Disclosure - Credit Risk - Summary of Modification of Loan Terms ( Consumer (Auto) Finance and Other Unsecured Lending) (Detail) Network

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1621 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
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1632 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
1633 1148 - Disclosure - Credit Risk - Summary of Consumer (Auto) Finance and Other Unsecured Lending by Forbearance (Detail) Network

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1634 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1636 Products and services [member] Member ifrs-full:ProductsAndServicesMember
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1638 Credit cards [member] Member ck0001087711:CreditCardsMember
1639 Overdrafts [member] Member ck0001087711:OverdraftsMember
1640 Total other unsecured [member] Member ck0001087711:TotalOtherUnsecuredMember
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1650 1149 - Disclosure - Credit Risk - Summary of Business Banking by Credit Performance (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfBusinessBankingByCreditPerformance
1651 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1666 Early Arrear Loans [member] Member ck0001087711:EarlyArrearLoansMember
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1669 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1670 Loss allowances Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
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1673 Gross write offs Concept (Monetary) For Period Debit ck0001087711:GrossWriteoffs
1674 1150 - Disclosure - Credit Risk - Summary of Modification of Loan Terms (Business Banking) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfModificationOfLoanTermsBusinessBanking
1675 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
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1677 Segments [member] Member ifrs-full:SegmentsMember
1678 Business Banking [member] Member ck0001087711:BusinessBankingMember
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1680 Amortised cost before modification Concept (Monetary) For Period Debit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesAmortisedCostBeforeModification
1681 Net modification loss Concept (Monetary) For Period Credit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesModificationGainLoss
1682 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
1683 1151 - Disclosure - Credit Risk - Summary of Business Banking by Forbearance (Detail) Network

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1684 Disclosure of credit risk exposure [table] Table

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ifrs-full:DisclosureOfCreditRiskExposureTable
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1693 Total value Concept (Monetary) As Of Debit ck0001087711:LoansForbearance
1694 1152 - Disclosure - Credit Risk - Summary of ECL Reconciliation For Other Business Segments (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfECLReconciliationForOtherBusinessSegments
1695 Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [table] Table

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*

ifrs-full:DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable
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1698 Financial instruments not credit-impaired [member] Member ifrs-full:FinancialInstrumentsNotCreditimpairedMember
1699 Financial instruments credit-impaired [member] Member ifrs-full:FinancialInstrumentsCreditimpairedMember
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1715 Subject to Lifetime ECL [member] Member ifrs-full:LifetimeExpectedCreditLossesMember
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1729 Transfer from credit impaired Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseThroughTransfersFromCreditImpairedFinancialAssets
1730 Transfers of financial instruments Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersFinancialAssets
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1732 New assets originated or purchased Concept (Monetary) For Period Debit ifrs-full:IncreaseThroughOriginationOrPurchaseFinancialAssets
1733 Other Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughOtherMovementsFinancialAssets
1734 Assets derecognised - closed good Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughDerecognitionFinancialAssets
1735 Assets derecognised - written off Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughWriteoffFinancialAssets
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1742 Income statement charge/(release) for the year Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
1743 1153 - Disclosure - Credit Risk - Summary of Other Segments Exposures by Credit Rating (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsExposuresByCreditRating
1744 Disclosure of credit risk exposure [table] Table

*

*

ifrs-full:DisclosureOfCreditRiskExposureTable
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1748 Internal grade 8 [member] Member ck0001087711:InternalGradeEightMember
1749 Internal grade 7 [member] Member ck0001087711:InternalGradeSevenMember
1750 Internal grade 6 [member] Member ck0001087711:InternalGradeSixMember
1751 Internal grade 5 [member] Member ck0001087711:InternalGradeFiveMember
1752 Internal grade 4 [member] Member ck0001087711:InternalGradeFourMember
1753 Internal grade 3 to 1 [member] Member ck0001087711:InternalGradeThreeToOneMember
1754 Other [member] Member ck0001087711:OtherInternalGradeMember
1755 Segments [axis] Axis ifrs-full:SegmentsAxis
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1757 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1758 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1759 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1760 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
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1762 SME and Mid Corporate [member] Member ck0001087711:SMEAndMidCorporateMember
1763 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstate1Member
1764 Social Housing [member] Member ck0001087711:SocialHousingMember
1765 Sovereign And Supranational [member] Member ck0001087711:SovereignAndSupranationalMember
1766 Large Corporate [member] Member ck0001087711:LargeCorporateMember
1767 Financial Institutions [member] Member ck0001087711:FinancialInstitutionsMember
1768 Structured Products [member] Member ck0001087711:StructuredProductsMember
1769 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
1770 Legacy Portfolios in Run-Off [member] Member ck0001087711:LegacyPortfoliosInRunoffMember
1771 Crown dependency branch [member] Member ck0001087711:CrownDependencyBranchMember
1772 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1773 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1774 Stage 1 [member] Member ck0001087711:StageOneMember
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1776 Stage 3 [member] Member ck0001087711:StageThreeMember
1777 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1778 Maximum exposure to credit risk Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1779 1154 - Disclosure - Credit Risk - Summary of Other Segments Exposures by Geographical Distribution (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsExposuresByGeographicalDistribution
1780 Disclosure of credit risk exposure [table] Table

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*

ifrs-full:DisclosureOfCreditRiskExposureTable
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1782 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
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1786 Rest Of World [member] Member ck0001087711:RestOfWorldMember
1787 Segments [axis] Axis ifrs-full:SegmentsAxis
1788 Segments [member] Member ifrs-full:SegmentsMember
1789 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1790 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1791 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1792 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1793 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1794 SME and Mid Corporate [member] Member ck0001087711:SMEAndMidCorporateMember
1795 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstate1Member
1796 Social Housing [member] Member ck0001087711:SocialHousingMember
1797 Sovereign And Supranational [member] Member ck0001087711:SovereignAndSupranationalMember
1798 Large Corporate [member] Member ck0001087711:LargeCorporateMember
1799 Financial Institutions [member] Member ck0001087711:FinancialInstitutionsMember
1800 Structured Products [member] Member ck0001087711:StructuredProductsMember
1801 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
1802 Legacy Portfolios in Run-Off [member] Member ck0001087711:LegacyPortfoliosInRunoffMember
1803 Crown dependency branch [member] Member ck0001087711:CrownDependencyBranchMember
1804 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1805 Maximum exposure to credit risk Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1806 1155 - Disclosure - Credit Risk - Summary of Other Segments Exposures by Credit Performance (Detail) Network

*

*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfOtherSegmentsExposuresByCreditPerformance
1807 Disclosure of credit risk exposure [table] Table

*

*

ifrs-full:DisclosureOfCreditRiskExposureTable
1808 Segments [axis] Axis ifrs-full:SegmentsAxis
1809 Segments [member] Member ifrs-full:SegmentsMember
1810 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1811 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1812 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1813 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1814 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1815 SME and Mid Corporate [member] Member ck0001087711:SMEAndMidCorporateMember
1816 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstate1Member
1817 Social Housing [member] Member ck0001087711:SocialHousingMember
1818 Sovereign And Supranational [member] Member ck0001087711:SovereignAndSupranationalMember
1819 Large Corporate [member] Member ck0001087711:LargeCorporateMember
1820 Financial Institutions [member] Member ck0001087711:FinancialInstitutionsMember
1821 Structured Products [member] Member ck0001087711:StructuredProductsMember
1822 Legacy Portfolios in Run-Off [member] Member ck0001087711:LegacyPortfoliosInRunoffMember
1823 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
1824 Crown dependency branch [member] Member ck0001087711:CrownDependencyBranchMember
1825 Observed Impairment Loss Allowances [Member] Member ck0001087711:ObservedImpairmentLossAllowancesMember
1826 Allowance for IBNO [member] Member ck0001087711:AllowanceForIBNOMember
1827 Method of assessment of expected credit losses [axis] Axis ifrs-full:MethodOfAssessmentOfExpectedCreditLossesAxis
1828 Method of assessment of expected credit losses [member] Member ifrs-full:MethodOfAssessmentOfExpectedCreditLossesMember
1829 Performing Exposure [member] Member ck0001087711:PerformingExposureMember
1830 Enhanced Monitoring [member] Member ck0001087711:EnhancedMonitoringMember
1831 Proactive Management [member] Member ck0001087711:ProactiveManagementMember
1832 Non-Performing Exposure [member] Member ck0001087711:NonperformingExposureMember
1833 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1834 Maximum exposure to credit risk Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1835 Observed impairment loss allowances Concept (Monetary) As Of Debit ck0001087711:AllowanceForObservedImpairmentLossesOnCreditExposure
1836 1156 - Disclosure - Credit Risk - Summary of Modification of Loan Terms (Other Segments Exposures) (Detail) Network

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1837 Disclosure of credit risk exposure [table] Table

*

*

ifrs-full:DisclosureOfCreditRiskExposureTable
1838 Segments [axis] Axis ifrs-full:SegmentsAxis
1839 Segments [member] Member ifrs-full:SegmentsMember
1840 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1841 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1842 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1843 Disclosure of credit risk exposure [line items] LineItems ifrs-full:DisclosureOfCreditRiskExposureLineItems
1844 Amortised cost before modification Concept (Monetary) For Period Debit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesAmortisedCostBeforeModification
1845 Net modification loss Concept (Monetary) For Period Credit ifrs-full:FinancialAssetsWithContractualCashFlowsModifiedDuringReportingPeriodWhileLossAllowanceMeasuredAtLifetimeExpectedCreditLossesModificationGainLoss
1846 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
1847 1157 - Disclosure - Credit Risk - Summary of Other Segments by Forbearance Applied (Detail) Network

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1848 Disclosure Of Forbearance [table] Table

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ck0001087711:DisclosureOfForbearanceTable
1849 Segments [axis] Axis ifrs-full:SegmentsAxis
1850 Segments [member] Member ifrs-full:SegmentsMember
1851 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1852 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
1853 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1854 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
1855 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
1856 Stage 1 [member] Member ck0001087711:StageOneMember
1857 Stage 2 [member] Member ck0001087711:StageTwoMember
1858 Stage 3 [member] Member ck0001087711:StageThreeMember
1859 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1860 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1861 Non-performing loans by forbearance [member] Member ck0001087711:NonPerformingLoansByForbearanceMember
1862 Performing [member] Member ck0001087711:PerformingForbearanceMember
1863 Disclosure Of Forbearance [line items] LineItems ck0001087711:DisclosureOfForbearanceLineItems
1864 - Term extension Concept (Monetary) As Of Debit ck0001087711:LoansTermExtensionForbearance
1865 - Interest-only Concept (Monetary) As Of Debit ck0001087711:LoansInterestOnlyForbearance
1866 - Other payment rescheduling Concept (Monetary) As Of Debit ck0001087711:LoansCapitalisationForbearance
1867 Loans forbearance Concept (Monetary) As Of Debit ck0001087711:LoansForbearance
1868 Proportion of portfolio Concept (Percent) As Of ck0001087711:LoansProportionOfPortfolioForbearancePercentage
1869 1158 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Credit Performance (Detail) Network

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1870 Disclosure of performance obligations [table] Table

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*

ifrs-full:DisclosureOfPerformanceObligationsTable
1871 Segments [axis] Axis ifrs-full:SegmentsAxis
1872 Segments [member] Member ifrs-full:SegmentsMember
1873 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstateSegmentMember
1874 Disclosure of performance obligations [line items] LineItems ifrs-full:DisclosureOfPerformanceObligationsLineItems
1875 Customer loans Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1876 NPLs Concept (Monetary) As Of Debit ck0001087711:NonPerformingLoans
1877 NPL ratio Concept (Percent) As Of ck0001087711:NonPerformingLoansRatio
1878 Gross write-offs Concept (Monetary) For Period Debit ck0001087711:GrossWriteoffs
1879 Impairment loss allowances Concept (Monetary) As Of Debit ck0001087711:ImpairmentLossAllowances
1880 1159 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Credit Performance (Parenthetical) (Detail) Network

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1881 Disclosure of performance obligations [table] Table

*

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ifrs-full:DisclosureOfPerformanceObligationsTable
1882 Segments [axis] Axis ifrs-full:SegmentsAxis
1883 Segments [member] Member ifrs-full:SegmentsMember
1884 Retail Banking Segment [member] Member ck0001087711:RetailBankingSegmentMember
1885 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstateSegmentMember
1886 Disclosure of performance obligations [line items] LineItems ifrs-full:DisclosureOfPerformanceObligationsLineItems
1887 Consumer loans Concept (Monetary) As Of Debit ifrs-full:ConsumerLoans
1888 1160 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Loan to Value (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureCreditRiskSummaryOfCommercialRealEstateByLoanToValue
1889 Disclosure Of Loan To Value [table] Table

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ck0001087711:DisclosureOfLoanToValueTable
1890 Segments [axis] Axis ifrs-full:SegmentsAxis
1891 Segments [member] Member ifrs-full:SegmentsMember
1892 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstate1Member
1893 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1894 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1895 Non performing loans [member] Member ck0001087711:NonPerformingLoansMember
1896 Range [axis] Axis ifrs-full:RangeAxis
1897 Ranges [member] Member ifrs-full:RangesMember
1898 Less Than Or Equal To Fifty Percentage [Member] Member ck0001087711:LessThanOrEqualToFiftyPercentageMember
1899 Greater than fifty percentage to seventy percentage [member] Member ck0001087711:GreaterThanFiftyPercentageToSeventyPercentageMember
1900 Greater Than 70-100% [member] Member ck0001087711:GreaterThanSeventyToHundredPercentageMember
1901 Greater Than 100% [member] Member ck0001087711:GreaterThanHundredPercentageMember
1902 Standardised Portfolio [member] Member ck0001087711:StandardizedPortfolioMember
1903 Total With Collateral [member] Member ck0001087711:CollateralMember
1904 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
1905 Products and services [member] Member ifrs-full:ProductsAndServicesMember
1906 Development Loans [member] Member ck0001087711:DevelopmentLoansMember
1907 Disclosure Of Loan To Value [line items] LineItems ck0001087711:DisclosureOfLoanToValueLineItems
1908 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1909 Percentage of loan to value Concept (Percent) As Of ck0001087711:PercentageOfLoanToValueStock
1910 1161 - Disclosure - Credit Risk - Summary of Commercial Real Estate by Sector (Detail) Network

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1911 Disclosure Of Loans And Advances By Industry Sector [table] Table

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ck0001087711:DisclosureOfLoansAndAdvancesByIndustrySectorTable
1912 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1913 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1914 Commercial Real Estate [member] Member ck0001087711:CommercialRealEstate1Member
1915 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
1916 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
1917 Office [member] Member ck0001087711:OfficeSectorMember
1918 Retail [member] Member ck0001087711:RetailMember
1919 Industrial [member] Member ck0001087711:IndustrialMember
1920 Residential [member] Member ck0001087711:ResidentialMember
1921 Mixed Use [member] Member ck0001087711:MixedUseMember
1922 Student Accommodation [member] Member ck0001087711:StudentLoansMember
1923 Hotels and Leisure [member] Member ck0001087711:HotelsAndLeisureMember
1924 Other [member] Member ck0001087711:OtherPortfolioMember
1925 Standardised Portfolio [member] Member ck0001087711:StandardizedPortfolioSectorMember
1926 Disclosure Of Loans And Advances By Industry Sector [line items] LineItems ck0001087711:DisclosureOfLoansAndAdvancesByIndustrySectorLineItems
1927 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1928 Percentage of total CRE Portfolio Concept (Percent) As Of ck0001087711:PercentageOfCommercialRealEstatePortfolio
1929 1162 - Disclosure - Credit Risk - Summary of Social Housing Exposure (Detail) Network

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1930 Disclosure Of Social Housing Exposure [table] Table

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ck0001087711:DisclosureOfSocialHousingExposureTable
1931 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
1932 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
1933 Social Housing [member] Member ck0001087711:SocialHousingMember
1934 Segments [axis] Axis ifrs-full:SegmentsAxis
1935 Segments [member] Member ifrs-full:SegmentsMember
1936 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
1937 Corporate centre [member] Member ck0001087711:CorporateCentreMember
1938 Disclosure Of Social Housing Exposure [line items] LineItems ck0001087711:DisclosureOfSocialHousingExposureLineItems
1939 Drawn Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1940 Total Concept (Monetary) As Of ifrs-full:MaximumExposureToCreditRisk
1941 1163 - Disclosure - Market Risk - Summary of Balance Sheet Allocation by Market Risk Classification (Detail) Network

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1942 Market Risk [table] Table

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ck0001087711:MarketRiskTable
1943 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
1944 Risks [member] Member ifrs-full:TypesOfRisksMember
1945 Banking Market Risk [member] Member ck0001087711:BankingMarketRiskMember
1946 Trading Market Risk [member] Member ck0001087711:TradingMarketRiskMember
1947 Market Risk [member] Member ifrs-full:MarketRiskMember
1948 Market Risk [line items] LineItems ck0001087711:MarketRiskLineItems
1949 Cash and balances at central banks Concept (Monetary) As Of Debit ifrs-full:CashAndBankBalancesAtCentralBanks
1950 - Trading assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
1951 - Derivative financial instruments Concept (Monetary) As Of Debit ifrs-full:DerivativeFinancialAssets
1952 - Other financial assets at FVTPL Concept (Monetary) As Of Debit ck0001087711:OtherFinancialAssetsAtFairValueThroughProfitOrLoss
1953 - Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
1954 - Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
1955 - Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ck0001087711:FinancialAssetsAtAmortisedCostReverseRepurchaseAgreementsNonTrading
1956 - Other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001087711:OtherFinancialAssetsAtAmortisedCost
1957 Financial assets at FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
1958 Financial investments Concept (Monetary) As Of Debit ck0001087711:FinancialInvestments
1959 Macro hedge of interest rate risk Concept (Monetary) As Of Debit ck0001087711:MacroHedgeOfInterestRateRisk
1960 Retirement benefit assets Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsDefinedBenefitPlan
1961 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
1962 - Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
1963 - Derivative financial instruments Concept (Monetary) As Of Credit ifrs-full:DerivativeFinancialLiabilities
1964 - Other financial liabilities at FVTPL Concept (Monetary) As Of Credit ck0001087711:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
1965 - Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
1966 - Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
1967 - Repurchase agreements - non trading Concept (Monetary) As Of Credit ck0001087711:FinancialLiabilitiesAtAmortisedCostRepurchaseAgreementsNonTrading
1968 - Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
1969 - Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
1970 Macro hedge of interest rate risk Concept (Monetary) As Of Credit ck0001087711:MacroHedgeOfInterestRateRiskLiability
1971 Retirement benefit obligations Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
1972 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
1973 1164 - Disclosure - Market Risk - Summary of Balance Sheet Allocation by Market Risk Classification (Parenthetical) (Detail) Network

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1974 Market Risk [table] Table

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ck0001087711:MarketRiskTable
1975 Classes of liabilities [axis] Axis ifrs-full:ClassesOfLiabilitiesAxis
1976 Liabilities [member] Member ifrs-full:LiabilitiesMember
1977 Other Liabilities [member] Member ck0001087711:OtherLiabilities1Member
1978 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
1979 Assets [member] Member ifrs-full:ClassesOfAssetsMember
1980 Other Assets [member] Member ifrs-full:OtherAssetsMember
1981 Market Risk [line items] LineItems ck0001087711:MarketRiskLineItems
1982 Macro hedge of interest rate risk including other assets Concept (Monetary) As Of Debit ck0001087711:MacroHedgeOfInterestRateRisk
1983 Macro hedge of interest rate risk including other liabilities Concept (Monetary) As Of Credit ck0001087711:MacroHedgeOfInterestRateRiskLiability
1984 1165 - Disclosure - Market Risk - Summary of NIM and EVE Sensitivity of Interest Rate Risk (Detail) Network

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1985 Disclosure Of Sensitivity Limit Of Risk [table] Table

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ck0001087711:DisclosureOfSensitivityLimitOfRiskTable
1986 Range [axis] Axis ifrs-full:RangeAxis
1987 Ranges [member] Member ifrs-full:RangesMember
1988 +50bps [member] Member ck0001087711:IncreaseOfFiftyBasisPointsMember
1989 -50bps [member] Member ck0001087711:DecreaseOfFiftyBasisPointsMember
1990 Disclosure Of Sensitivity Limit Of Risk [line items] LineItems ck0001087711:DisclosureOfSensitivityLimitOfRiskLineItems
1991 NIM sensitivity Concept (Monetary) As Of Debit ck0001087711:NIMSensitivityRiskLimit
1992 EVE sensitivity (unaudited) Concept (Monetary) As Of Debit ck0001087711:EVESensitivityRiskLimit
1993 1166 - Disclosure - Market Risk - Summary of NIM and EVE Sensitivity of Interest Rate Risk (Parenthetical) (Detail) Network

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1994 Disclosure Of Sensitivity Limit Of Risk [table] Table

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ck0001087711:DisclosureOfSensitivityLimitOfRiskTable
1995 Range [axis] Axis ifrs-full:RangeAxis
1996 Ranges [member] Member ifrs-full:RangesMember
1997 +50bps [member] Member ck0001087711:IncreaseOfFiftyBasisPointsMember
1998 -50bps [member] Member ck0001087711:DecreaseOfFiftyBasisPointsMember
1999 Disclosure Of Sensitivity Limit Of Risk [line items] LineItems ck0001087711:DisclosureOfSensitivityLimitOfRiskLineItems
2000 Shift in basis point Concept (Percent) As Of ck0001087711:ShiftInBasisPoint
2001 1167 - Disclosure - Market Risk - Summary of Internal VaR for Exposure to Main Classes of Risk (Detail) Network

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2002 Market Risk [table] Table

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ck0001087711:MarketRiskTable
2003 Range [axis] Axis ifrs-full:RangeAxis
2004 Ranges [member] Member ifrs-full:RangesMember
2005 Weighted average [member] Member ifrs-full:WeightedAverageMember
2006 Top of Range [member] Member ifrs-full:TopOfRangeMember
2007 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2008 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2009 Risks [member] Member ifrs-full:TypesOfRisksMember
2010 Interest Rate Risks [member] Member ifrs-full:InterestRateRiskMember
2011 Equity Risks [member] Member ifrs-full:EquityPriceRiskMember
2012 Currency Risk [member] Member ifrs-full:CurrencyRiskMember
2013 Diversification Offsets [member] Member ifrs-full:RiskDiversificationEffectMember
2014 Market Risk [line items] LineItems ck0001087711:MarketRiskLineItems
2015 Risk exposure Concept (Monetary) As Of ifrs-full:ValueAtRisk
2016 1168 - Disclosure - Liquidity Risk - Summary of Reconciliation of Wholesale Funding to Balance Sheet (Detail) Network

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2017 Reconciliation Of Wholesale Funding To Balance Sheet [table] Table

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ck0001087711:ReconciliationOfWholesaleFundingToBalanceSheetTable
2018 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2019 Risks [member] Member ifrs-full:TypesOfRisksMember
2020 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2021 Cash And Cash Equivalents 1 [axis] Axis ck0001087711:CashAndCashEquivalents1Axis
2022 Share-based Incentive Plans [member] Member ck0001087711:SharebasedIncentivePlansMember
2023 Wholesale Funding [member] Member ck0001087711:WholesaleFundingMember
2024 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2025 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2026 Deposits [member] Member ck0001087711:Deposits1Member
2027 Certificates of Deposit and Commercial Paper [member] Member ck0001087711:CertificatesOfDepositAndCommercialPaperMember
2028 Senior Unsecured - Public Benchmark [member] Member ck0001087711:SeniorUnsecuredPublicBenchmarkMember
2029 Senior Unsecured - Privately Placed [member] Member ck0001087711:SeniorUnsecuredPrivatelyPlacedMember
2030 Covered Bonds [member] Member ck0001087711:CoveredBondsMember
2031 Securitisation and Structured Issuance [member] Member ck0001087711:SecuritisationAndStructuredIssuanceMember
2032 Term Funding Scheme [member] Member ck0001087711:TermFundingSchemeMember
2033 Subordinated Liabilities and Equity [member] Member ck0001087711:SubordinatedLiabilitiesAndEquityMember
2034 Repurchase Agreement [member] Member ck0001087711:RepurchaseAgreementMember
2035 Foreign Exchange And Hedge Accounting [member] Member ck0001087711:ForeignExchangeAndHedgeAccountingMember
2036 Other Borrowing [Member] Member ck0001087711:OtherBorrowingMember
2037 Reconciliation Of Wholesale Funding To Balance Sheet [line items] LineItems ck0001087711:ReconciliationOfWholesaleFundingToBalanceSheetLineItems
2038 Funding analysis Concept (Monetary) As Of Credit ck0001087711:FundingAnalysis
2039 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2040 Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
2041 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
2042 Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
2043 Financial liabilities at fair value Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
2044 Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
2045 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
2046 Other equity and non-controlling interests Concept (Monetary) As Of Credit ck0001087711:OtherEquityAndNoncontrollingInterests
2047 1169 - Disclosure - Liquidity Risk - Summary of Reconciliation of Wholesale Funding to Balance Sheet (Parenthetical) (Detail) Network

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2048 Reconciliation Of Wholesale Funding To Balance Sheet [table] Table

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ck0001087711:ReconciliationOfWholesaleFundingToBalanceSheetTable
2049 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
2050 Equity [member] Member ifrs-full:EquityMember
2051 Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001087711:NoncumulativeCallablePreferenceSharesMember
2052 Step-Up Callable Perpetual Reserve Capital Instruments [member] Member ck0001087711:StepupCallablePerpetualReserveCapitalInstrumentsMember
2053 Perpetual Capital Securities [member] Member ck0001087711:PerpetualCapitalSecuritiesMember
2054 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2055 Risks [member] Member ifrs-full:TypesOfRisksMember
2056 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2057 Reconciliation Of Wholesale Funding To Balance Sheet [line items] LineItems ck0001087711:ReconciliationOfWholesaleFundingToBalanceSheetLineItems
2058 Deposit from customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
2059 Other equity and non-controlling interests Concept (Monetary) As Of Credit ifrs-full:OtherEquityInterest
2060 1170 - Disclosure - Liquidity Risk - Summary of Sources of Wholesale Funding by Maturity (Detail) Network

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2061 Disclosure of Sources of Wholesale Funding [table] Table

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ck0001087711:DisclosureOfSourcesOfWholesaleFundingTable
2062 Maturity [axis] Axis ifrs-full:MaturityAxis
2063 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2064 Not Later Than One Month [member] Member ifrs-full:NotLaterThanOneMonthMember
2065 Greater Than 1 and Less Than 3 Months [member] Member ifrs-full:LaterThanOneMonthAndNotLaterThanThreeMonthsMember
2066 Greater Than 3 and Less Than 6 Months [member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanSixMonthsMember
2067 Greater Than 6 and Less Than 9 Months [member] Member ck0001087711:LaterThanSixMonthsAndNotLaterThanNineMonthsMember
2068 Greater Than 9 and Less Than 12 Months [member] Member ck0001087711:LaterThanNineMonthsAndNotLaterThanOneYearMember
2069 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2070 Later Than 1 Year and Not Later Than 2 Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
2071 Later Than 2 Year and Not Later Than 5 Years [member] Member ifrs-full:LaterThanTwoYearsAndNotLaterThanFiveYearsMember
2072 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
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2074 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
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2076 Other Santander UK Plc [member] Member ck0001087711:OtherSantanderUKPlcMember
2077 Other Group Entities [member] Member ck0001087711:OtherGroupEntitiesMember
2078 Disclosure of Maturity of Wholesale Funding [Line Items] LineItems ck0001087711:DisclosureOfSourcesOfWholesaleFundingLineItems
2079 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2080 Certificates of deposit and commercial paper Concept (Monetary) As Of Credit ck0001087711:CertificatesOfDepositAndCommercialPaper
2081 Senior unsecured - public benchmark Concept (Monetary) As Of Credit ck0001087711:SeniorUnsecuredPublicBenchmark
2082 Senior unsecured - privately placed Concept (Monetary) As Of Credit ck0001087711:SeniorUnsecuredPrivatelyPlaced
2083 Covered bonds Concept (Monetary) As Of Credit ck0001087711:CoveredBonds
2084 Subordinated liabilities and equity (incl. AT1) Concept (Monetary) As Of Credit ck0001087711:SubordinatedLiabilitiesAndEquity
2085 Securitisation and structured issuance Concept (Monetary) As Of Credit ck0001087711:SecuritisationAndStructuredIssuance
2086 Term Funding Scheme Concept (Monetary) As Of Credit ck0001087711:TermFundingScheme
2087 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
2088 Wholesale fund amount Concept (Monetary) As Of Credit ck0001087711:WholesaleFundAmount
2089 Of which: - secured Concept (Monetary) As Of Credit ck0001087711:SecuredWholesaleFundAmount
2090 Of which: - unsecured Concept (Monetary) As Of Credit ck0001087711:UnsecuredWholesaleFundAmount
2091 1171 - Disclosure - Liquidity Risk - Summary of Wholesale Funding by Currency (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureLiquidityRiskSummaryOfWholesaleFundingByCurrency
2092 Currency Composition Of Wholesale Funds [table] Table

*

*

ck0001087711:CurrencyCompositionOfWholesaleFundsTable
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2096 United States of America, Dollars [member] Member currency:USD
2097 Euro Member Countries, Euro [member] Member currency:EUR
2098 Other [member] Member ck0001087711:OtherCurrenciesMember
2099 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2100 Risks [member] Member ifrs-full:TypesOfRisksMember
2101 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2102 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
2103 Counterparties [member] Member ifrs-full:CounterpartiesMember
2104 Downstreamed From Santander UK Group Holdings Plc to Santander UK Plc [member] Member ck0001087711:DownstreamedFromSantanderUKGroupHoldingsPlcToSantanderUKPlcMember
2105 Other Santander UK Plc [member] Member ck0001087711:OtherSantanderUKPlcMember
2106 Other Group Entities [member] Member ck0001087711:OtherGroupEntitiesMember
2107 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2108 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2109 Senior Unsecured - Public Benchmark [member] Member ck0001087711:SeniorUnsecuredPublicBenchmarkMember
2110 Senior Unsecured - Privately Placed [member] Member ck0001087711:SeniorUnsecuredPrivatelyPlacedMember
2111 Subordinated Liabilities and Equity [member] Member ck0001087711:SubordinatedLiabilitiesAndEquityMember
2112 Deposits by banks [member] Member ck0001087711:DepositsByBanksMember
2113 Certificates of Deposit and Commercial Paper [member] Member ck0001087711:CertificatesOfDepositAndCommercialPaperMember
2114 Covered Bonds [member] Member ck0001087711:CoveredBondsMember
2115 Securitisation and Structured Issuance [member] Member ck0001087711:SecuritisationAndStructuredIssuanceMember
2116 Term Funding Scheme [member] Member ck0001087711:TermFundingSchemeMember
2117 Subordinated liabilities [member] Member ck0001087711:SubordinatedLiabilitiesMember
2118 Currency Composition Of Wholesale Funds [line items] LineItems ck0001087711:CurrencyCompositionOfWholesaleFundsLineItems
2119 Percentage of wholesale funding by major currencies Concept (Percent) As Of ck0001087711:PercentageOfWholesaleFundingByCurrencies
2120 1172 - Disclosure - Liquidity Risk - Summary of External Term Issuance (Sterling Equivalent) (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureLiquidityRiskSummaryOfExternalTermIssuanceSterlingEquivalent
2121 Disclosure of detailed information about borrowings [table] Table

*

*

ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
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2123 All Currencies [Domain] Member currency:AllCurrenciesDomain
2124 United Kingdom, Pounds [member] Member currency:GBP
2125 United States of America, Dollars [member] Member currency:USD
2126 Euro Member Countries, Euro [member] Member currency:EUR
2127 Types of risks [axis] Axis ifrs-full:TypesOfRisksAxis
2128 Risks [member] Member ifrs-full:TypesOfRisksMember
2129 Liquidity risk [member] Member ifrs-full:LiquidityRiskMember
2130 Counterparties [axis] Axis ifrs-full:CounterpartiesAxis
2131 Counterparties [member] Member ifrs-full:CounterpartiesMember
2132 Downstreamed From Santander UK Group Holdings Plc to Santander UK Plc [member] Member ck0001087711:DownstreamedFromSantanderUKGroupHoldingsPlcToSantanderUKPlcMember
2133 Other Santander UK Plc [member] Member ck0001087711:OtherSantanderUKPlcMember
2134 Other Group Entities [member] Member ck0001087711:OtherGroupEntitiesMember
2135 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
2136 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
2137 Senior Unsecured - Public Benchmark [member] Member ck0001087711:SeniorUnsecuredPublicBenchmarkMember
2138 Senior Unsecured - Privately Placed [member] Member ck0001087711:SeniorUnsecuredPrivatelyPlacedMember
2139 Subordinated Liabilities and Equity [member] Member ck0001087711:SubordinatedLiabilitiesAndEquityMember
2140 Securitisations [member] Member ifrs-full:SecuritisationsMember
2141 Covered Bonds [member] Member ck0001087711:CoveredBondsMember
2142 Term Funding Scheme [member] Member ck0001087711:TermFundingSchemeMember
2143 Disclosure of detailed information about borrowings [line items] LineItems ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
2144 Borrowings Concept (Monetary) As Of Credit ifrs-full:Borrowings
2145 1173 - Disclosure - Capital Risk - Summary of Regulatory Capital Resources (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureCapitalRiskSummaryOfRegulatoryCapitalResources
2146 Disclosure Of Regulatory Capital Resources [table] Table

*

*

ck0001087711:DisclosureOfRegulatoryCapitalResourcesTable
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2148 Components Of Regulatory Capital [member] Member ck0001087711:ComponentsOfRegulatoryCapitalMember
2149 Tier Two Capital [member] Member ck0001087711:TierTwoCapitalMember
2150 Disclosure of Regulatory Capital Resources [Line Items] LineItems ck0001087711:DisclosureOfRegulatoryCapitalResourcesLineItems
2151 CET1 capital Concept (Monetary) As Of Credit ck0001087711:CommonEquityTierOneCapitalAmount
2152 AT1 capital Concept (Monetary) As Of Credit ck0001087711:AdditionalTierOneCapital
2153 Tier 1 capital Concept (Monetary) As Of Credit ck0001087711:TierOneCapitalAmount
2154 Total regulatory capital Concept (Monetary) As Of Debit ck0001087711:RegulatoryCapital
2155 1174 - Disclosure - Accounting Policies - Additional information (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureAccountingPoliciesAdditionalInformation
2156 Disclosure of changes in accounting estimates [table] Table

*

*

ifrs-full:DisclosureOfChangesInAccountingEstimatesTable
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2159 Stage 2 [member] Member ck0001087711:StageTwoMember
2160 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
2161 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
2162 IFRS 16 [member] Member ck0001087711:IFRS16Member
2163 IFRS 9 [member] Member ck0001087711:IFRS9Member
2164 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
2165 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
2166 House price index [Member] Member ck0001087711:HousePriceIndexMember
2167 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2168 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2169 Santandar UK plc [member] Member ck0001087711:CompanyMember
2170 Amounts arising from insurance contracts [axis] Axis ifrs-full:AmountsArisingFromInsuranceContractsAxis
2171 Net amount arising from insurance contracts [member] Member ifrs-full:NetAmountArisingFromInsuranceContractsMember
2172 Payment protection insurance [member] Member ck0001087711:PaymentProtectionInsuranceMember
2173 Past due status [axis] Axis ifrs-full:PastDueStatusAxis
2174 Past due status [member] Member ifrs-full:PastDueStatusMember
2175 180 Days [member] Member ck0001087711:OneHundredAndEightyDaysMember
2176 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2177 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2178 Unsecured Debt [member] Member ck0001087711:UnsecuredDebt1Member
2179 Segments [axis] Axis ifrs-full:SegmentsAxis
2180 Segments [member] Member ifrs-full:SegmentsMember
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2182 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
2183 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
2184 Other provisions [member] Member ifrs-full:OtherProvisionsMember
2185 Miscellaneous other provisions [member] Member ifrs-full:MiscellaneousOtherProvisionsMember
2186 Disclosure of changes in accounting estimates [line items] LineItems ifrs-full:DisclosureOfChangesInAccountingEstimatesLineItems
2187 Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
2188 Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
2189 Deposit by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
2190 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
2191 Increase Property, plant and equipment Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreasePropertyPlantAndEquipment
2192 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
2193 Other liabilities Concept (Monetary) As Of Credit ifrs-full:OtherLiabilities
2194 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
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2196 Expected credit losses allowance Concept (Monetary) For Period Credit ck0001087711:ExpectedCreditLossesAllowance
2197 Probability weight Concept (Percent) For Period ck0001087711:ProbabilityWeightedAverageOfExpectedCreditLosses
2198 Expected credit losses allowance for residential mortgages Concept (Monetary) For Period Credit ck0001087711:ExpectedCreditLossesAllowanceForResidentialMortgages
2199 Additional provisions Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
2200 Additional operational risk losses and restructuring charges Concept (Monetary) For Period Credit ck0001087711:AdditionalProvisionsOtherProvisionsOperationalRiskLossesAndRestructuringCharges
2201 Defined benefit pension schemes in net asset having surplus Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsDefinedBenefitPlan
2202 Defined benefit pension schemes in net liabilities having deficit Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
2203 1175 - Disclosure - Accounting Policies - Summary of Useful Lives or Depreciation Rates Used for Property, Plant and Equipment (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureAccountingPoliciesSummaryOfUsefulLivesOrDepreciationRatesUsedForPropertyPlantAndEquipment
2204 Disclosure of detailed information about property, plant and equipment [table] Table

*

*

ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
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2206 Ranges [member] Member ifrs-full:RangesMember
2207 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2208 Top of Range [member] Member ifrs-full:TopOfRangeMember
2209 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
2210 Property, plant and equipment [member] Member ifrs-full:PropertyPlantAndEquipmentMember
2211 Owner-occupied properties [member] Member ck0001087711:OwnerOccupiedPropertiesMember
2212 Office Fixtures and Equipment [member] Member ck0001087711:OfficeFixturesAndEquipmentMember
2213 Computer Software [member] Member ifrs-full:ComputerSoftwareMember
2214 Disclosure of detailed information about property, plant and equipment [line items] LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
2215 Useful lives or depreciation rates, property, plant and equipment Concept (xbrli:durationItemType) For Period ck0001087711:UsefulLivesPropertyPlantAndEquipment
2216 1176 - Disclosure - Accounting Policies - Summary of Probability Weights Applied for Each Scenario of Expected Credit Losses Allowance (Detail) Network

*

*

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2217 Disclosure of probability weightings of scenarios [table] Table

*

*

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2218 Project by scenario [axis] Axis ck0001087711:ProjectByScenarioAxis
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2221 Upside 1 [member] Member ck0001087711:UpsideOneScenarioMember
2222 Base case [member] Member ck0001087711:BaseCaseScenarioMember
2223 Downside 1 [member] Member ck0001087711:DownsideOneScenarioMember
2224 Downside 2 [member] Member ck0001087711:DownsideTwoScenarioMember
2225 Downside [member] Member ck0001087711:DownsideMember
2226 Upside [member] Member ck0001087711:UpsideMember
2227 Segments [axis] Axis ifrs-full:SegmentsAxis
2228 Segments [member] Member ifrs-full:SegmentsMember
2229 Retail banking Corporate and Commercial Banking and Corporate Centre [member] Member ck0001087711:RetailBankingCorporateAndCommercialBankingAndCorporateCentreMember
2230 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
2231 Disclosure of probability weightings of scenarios [line items] LineItems ck0001087711:DisclosureOfProbabilityWeightingsOfScenariosLineItems
2232 ECL Concept (Monetary) For Period Credit ck0001087711:ExpectedCreditLossesAllowance
2233 1177 - Disclosure - Accounting Policies - Summary of Increase (Decrease in Profit Before Tax (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureAccountingPoliciesSummaryOfIncreaseDecreaseInProfitBeforeTax
2234 Implied Table Table

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*

implied:Table
2235 Disclosure - Accounting Policies - Summary of Increase (Decrease in Profit Before Tax [Abstract] Abstract ck0001087711:DisclosureAccountingPoliciesSummaryOfIncreaseDecreaseInProfitBeforeTaxAbstract
2236 Increase in profit before tax due to 20 percentage increase in HPI rate Concept (Monetary) For Period Credit ck0001087711:ProfitBeforeTaxDueToTwentyPercentageIncreaseInHpiRate
2237 Increase in profit before tax due to 10 percentage increase in HPI rate Concept (Monetary) For Period Credit ck0001087711:ProfitBeforeTaxDueToTenPercentageIncreaseInHpiRate
2238 Decrease in profit before tax due to 10 percentage decrease in HPI rate Concept (Monetary) For Period Credit ck0001087711:ProfitBeforeTaxDueToTenPercentageDecreaseInHpiRate
2239 Decrease in profit before tax due to 20 percentage decrease in HPI rate Concept (Monetary) For Period Credit ck0001087711:ProfitBeforeTaxDueToTwentyPercentageDecreaseInHpiRate
2240 1178 - Disclosure - Segments - Additional Information (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureSegmentsAdditionalInformation
2241 Disclosure of operating segments [table] Table

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*

ifrs-full:DisclosureOfOperatingSegmentsTable
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2246 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
2247 Range [axis] Axis ifrs-full:RangeAxis
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2249 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2250 Top of Range [member] Member ifrs-full:TopOfRangeMember
2251 Disclosure of operating segments [line items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2252 Turnover from Small business customers Concept (Monetary) For Period Credit ck0001087711:TurnoverFromSmallBusinessCustomers
2253 Annual turnover of business Concept (Monetary) For Period Credit ck0001087711:TurnoverFromMediumAndLargeBusinessCustomers
2254 1179 - Disclosure - Segments - Summary of Results by Segment (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSegmentsSummaryOfResultsBySegment
2255 Disclosure of operating segments [table] Table

*

*

ifrs-full:DisclosureOfOperatingSegmentsTable
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2259 Corporate and commercial banking [member] Member ck0001087711:CorporateAndCommercialBankingMember
2260 Corporate and investment banking [member] Member ck0001087711:CorporateAndInvestmentBankingMember
2261 Corporate centre [member] Member ck0001087711:CorporateCentreMember
2262 Segment consolidation items [axis] Axis ifrs-full:SegmentConsolidationItemsAxis
2263 Entity's total for segment consolidation items [member] Member ifrs-full:EntitysTotalForSegmentConsolidationItemsMember
2264 Elimination of Intersegment Amounts [member] Member ifrs-full:EliminationOfIntersegmentAmountsMember
2265 Disclosure of operating segments [line items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
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2267 Non-interest income Concept (Monetary) For Period Credit ck0001087711:NonInterestIncomeExpense
2268 Total operating income Concept (Monetary) For Period Credit ck0001087711:AggregateOperatingIncomeExpense
2269 Operating expenses before credit impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001087711:OperatingExpensesBeforeCreditImpairmentLossesProvisionsAndCharges
2270 Credit impairment (losses)/releases Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
2271 Provisions for other liabilities and charges Concept (Monetary) For Period Debit ck0001087711:ProvisionsForOtherLiabilitiesAndCharges
2272 Total operating credit impairment losses, provisions and (charges)/releases Concept (Monetary) For Period Debit ck0001087711:AggregateOperatingCreditImpairmentLossesProvisionsAndCharges
2273 Profit before tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2274 Revenue from external customers Concept (Monetary) For Period Credit ifrs-full:RevenueFromContractsWithCustomers
2275 Inter-segment revenue Concept (Monetary) For Period Credit ifrs-full:RevenueAndOperatingIncome
2276 Total operating income Concept (Monetary) For Period Credit ck0001087711:AggregateOperatingIncomeExpense
2277 Revenue from external customers includes the following fee and commission income disaggregated by income type: Abstract ifrs-full:ReceivablesFromContractsWithCustomersAbstract
2278 - Current account and debit card fees Concept (Monetary) For Period Credit ck0001087711:IncomeFromCurrentAccountAndDebitCardFees
2279 - Insurance, protection and investments Concept (Monetary) For Period Credit ck0001087711:IncomeFromInsuranceProtectionAndInvestments
2280 - Credit cards Concept (Monetary) For Period Credit ck0001087711:IncomeFromCreditCards
2281 - Non-banking and other fees(3) Concept (Monetary) For Period Credit ck0001087711:IncomeFromNonBankingAndOtherFees
2282 Total fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncome
2283 Fee and commission expense Concept (Monetary) For Period Debit ifrs-full:FeeAndCommissionExpense
2284 Net fee and commission income Concept (Monetary) For Period Credit ck0001087711:FeeAndCommissionIncomeExpenseNet
2285 Customer loans Concept (Monetary) As Of Debit ck0001087711:CustomerLoansNet
2286 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
2287 Customer deposits Concept (Monetary) As Of Credit ck0001087711:CustomerDepositsNet
2288 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
2289 Average number of staff Concept (Decimal) For Period ifrs-full:AverageNumberOfEmployees
2290 1180 - Disclosure - Segments - Summary of Results by Segment (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSegmentsSummaryOfResultsBySegmentParenthetical
2291 Disclosure of operating segments [table] Table

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*

ifrs-full:DisclosureOfOperatingSegmentsTable
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2296 Segments [member] Member ifrs-full:SegmentsMember
2297 Corporate centre [member] Member ck0001087711:CorporateCentreMember
2298 Disclosure of operating segments [line items] LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2299 Profit before tax Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2300 Customer loans Concept (Monetary) As Of Debit ck0001087711:CustomerLoansNet
2301 Customer deposits Concept (Monetary) As Of Credit ck0001087711:CustomerDepositsNet
2302 1181 - Disclosure - Net Interest Income - Summary of Net Interest Income (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureNetInterestIncomeSummaryOfNetInterestIncome
2303 Implied Table Table

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*

implied:Table
2304 Analysis of income and expense [abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
2305 Interest and similar income: Abstract ck0001087711:InterestAndSimilarIncomeAbstract
2306 Loans and advances to customers Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnLoansAndAdvancesToCustomers
2307 Loans and advances to banks Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnLoansAndAdvancesToBanks
2308 Reverse repurchase agreements - non trading Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
2309 Other Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnOtherFinancialAssets
2310 Total interest and similar income Concept (Monetary) For Period Credit ifrs-full:RevenueFromInterest
2311 Interest expense and similar charges: Abstract ck0001087711:InterestExpenseAndSimilarChargesAbstract
2312 Deposits by customers Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnDepositsFromCustomers
2313 Deposits by banks Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnDepositsFromBanks
2314 Repurchase agreements - non trading Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnRepurchaseAgreementsAndCashCollateralOnSecuritiesLent
2315 Debt securities in issue Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnDebtInstrumentsIssued
2316 Subordinated liabilities Concept (Monetary) For Period Debit ck0001087711:InterestExpenseOnSubordinatedLiabilities
2317 Other Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnOtherFinancialLiabilities
2318 Total interest expense and similar charges Concept (Monetary) For Period Debit ifrs-full:InterestExpense
2319 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestRevenueExpense
2320 1182 - Disclosure - Net Interest Income - Summary of Net Interest Income (Parenthetical) (Detail) Network

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2321 Implied Table Table

*

*

implied:Table
2322 Analysis of income and expense [abstract] Abstract ifrs-full:AnalysisOfIncomeAndExpenseAbstract
2323 Interest income on financial assets at fair value through other comprehensive income Concept (Monetary) For Period Credit ifrs-full:InterestIncomeForFinancialAssetsNotAtFairValueThroughProfitOrLoss
2324 Interest expense on financial assets at fair value through other comprehensive income Concept (Monetary) For Period Debit ck0001087711:InterestExpenseNotAtFairValueThroughProfitOrLoss
2325 1183 - Disclosure - Net Interest Income - Additional Information (Detail) Network

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*

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2326 Implied Table Table

*

*

implied:Table
2327 Interest And Similar Income [abstract] Abstract ck0001087711:InterestAndSimilarIncomeAbstract
2328 Interest and similar income on impaired loans Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnImpairedFinancialAssetsAccrued
2329 1184 - Disclosure - Net Fee and Commission Income - Summary of Net Fee and Commission Income (Detail) Network

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2330 Disclosure of disaggregation of revenue from contracts with customers [table] Table

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*

ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersTable
2331 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
2332 Products and services [member] Member ifrs-full:ProductsAndServicesMember
2333 Current account and debit card fees [member] Member ck0001087711:CurrentAccountAndDebitCardFeesMember
2334 Insurance, protection and investments [member] Member ck0001087711:InsuranceProtectionAndInvestmentsMember
2335 Credit cards [member] Member ck0001087711:CreditCardsMember
2336 Non-banking and other fees [member] Member ck0001087711:NonbankingAndOtherFeesMember
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2338 Fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncome
2339 Fee and commission expense Concept (Monetary) For Period Debit ifrs-full:FeeAndCommissionExpense
2340 Net fee and commission income Concept (Monetary) For Period Credit ifrs-full:FeeAndCommissionIncomeExpense
2341 1185 - Disclosure - Net Trading and Other Income - Summary of Net Trading and Other Income (Detail) Network

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2342 Implied Table Table

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2343 Net Trading And Other Income [abstract] Abstract ck0001087711:NetTradingAndOtherIncomeAbstract
2344 Net trading and funding of other items by the trading book Concept (Monetary) For Period Credit ifrs-full:OtherTradingIncomeExpense
2345 Net (losses)/ gains on other financial assets at fair value through profit or loss Concept (Monetary) For Period Credit ck0001087711:GainsLossesOnOtherFinancialAssetsAtFairValueThroughProfitOrLoss
2346 Net (losses)/gains on other financial liabilities at fair value through profit or loss Concept (Monetary) For Period Credit ck0001087711:GainsLossesOnOtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
2347 Net losses on derivatives managed with assets/liabilities held at fair value through profit or loss Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnChangeInFairValueOfDerivatives
2348 Hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectiveness
2349 Net profit on sale of available-for-sale assets Concept (Monetary) For Period Credit ck0001087711:GainsLossesFromDisposalOfAvailableForSaleFinancialAssets
2350 Net profit on sale of financial assets at fair value through other comprehensive income Concept (Monetary) For Period Credit ck0001087711:GainsLossesOnSaleFromDisposalOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
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2352 Other Concept (Monetary) For Period Credit ifrs-full:OtherIncome
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2354 1186 - Disclosure - Net Trading and Other Income - Additional Information (Detail) Network

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2355 Disclosure of Subordinated Liabilities [table] Table

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2356 Legal entity [axis] Axis dei:LegalEntityAxis
2357 Entity [Domain] Member dei:EntityDomain
2358 Vocalink Holdings Limited [member] Member ck0001087711:VocalinkHoldingsLimitedMember
2359 Visa Europe Ltd [member] Member ck0001087711:VisaEuropeLtdMember
2360 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
2361 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
2362 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
2363 Non-Cumulative Trust Preferred Securities [member] Member ck0001087711:NoncumulativeTrustPreferredSecuritiesMember
2364 Disclosure of subordinated liabilities [line items] LineItems ck0001087711:DisclosureOfSubordinatedLiabilitiesLineItems
2365 Fair value gains/(losses) on net trading and funding of other items by trading book Concept (Monetary) For Period Debit ck0001087711:FairValueLossesOnNetTradingAndFundingOfOtherItemsByTradingBook
2366 (Losses)/gains on equity derivatives trading desk Concept (Monetary) For Period Credit ck0001087711:GainsOnEquityDerivativesTradingDesk
2367 Net gain on equity index-linked deposits and the related economic hedges Concept (Monetary) For Period Credit ck0001087711:NetGainOnEquityIndexlinkedDepositsAndTheRelatedEconomicHedges
2368 Gain on sale of shares Concept (Monetary) For Period Credit ck0001087711:GainOnSaleOfEquitySecurities
2369 Percentage of notes purchased and redeemed Concept (Percent) As Of ck0001087711:RedemptionPercentage
2370 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
2371 Maturity year Concept (Text/String) For Period ck0001087711:CallDateOfUndatedSubordinatedLiabilities
2372 Exchange rate differences recognised Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
2373 Principally offset from cash flow hedge reserve Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax
2374 1187 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Summary of Operating Expenses Before Credit Impairment Losses, Provisions and Charges (Detail) Network

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2375 Implied Table Table

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2376 Expenses by nature [abstract] Abstract ifrs-full:ExpenseByNatureAbstract
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2379 Performance-related payments Concept (Monetary) For Period Debit ck0001087711:PerformanceRelatedPayments
2380 Social security costs Concept (Monetary) For Period Debit ifrs-full:SocialSecurityContributions
2381 Pensions costs - defined contribution plans Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
2382 Pensions costs - defined benefit plans Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedBenefitPlans
2383 Other share-based payments Concept (Monetary) For Period Debit ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
2384 Other personnel costs Concept (Monetary) For Period Debit ifrs-full:OtherEmployeeExpense
2385 Employee benefits expense Concept (Monetary) For Period Debit ifrs-full:EmployeeBenefitsExpense
2386 Other administration expenses Concept (Monetary) For Period Debit ck0001087711:OtherAdministrationExpenses
2387 Depreciation, amortisation and impairment Concept (Monetary) For Period Debit ifrs-full:DepreciationAmortisationAndImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLoss
2388 Total operating expenses before impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001087711:OperatingExpensesBeforeCreditImpairmentLossesProvisionsAndCharges
2389 1188 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Summary of Deferred Performance Awards (Detail) Network

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2390 Disclosure of Deferred Performance Awards [table] Table

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2392 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2393 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2394 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
2395 Year In Which Awards Arose [axis] Axis ck0001087711:YearInWhichAwardsAroseAxis
2396 Year In Which Awards Arose [domain] Member ck0001087711:YearInWhichAwardsAroseDomain
2397 Arising From Awards in Current Year [member] Member ifrs-full:CurrentMember
2398 Arising From Awards in Prior Year [member] Member ck0001087711:PriorPeriodMember
2399 Disclosure of deferred performance awards [line Items] LineItems ck0001087711:DisclosureOfDeferredPerformanceAwardsLineItems
2400 Cash Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsCashDeferred
2401 Shares Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsSharesDeferred
2402 Deferred performance awards Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsDeferred
2403 1189 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Summary of Amount of Bonus Awarded to Employees (Detail) Network

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2404 Disclosure of Amount of Bonus Awarded to Employees [table] Table

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ck0001087711:DisclosureOfAmountOfBonusAwardedToEmployeesTable
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2406 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2407 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2408 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
2409 Disclosure of amount of bonus awarded to employees [line items] LineItems ck0001087711:DisclosureOfAmountOfBonusAwardedToEmployeesLineItems
2410 Cash award - not deferred Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsCashNonDeferred
2411 - deferred Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsCashDeferred
2412 Share awards - not deferred Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsSharesNonDeferred
2413 - deferred Concept (Monetary) For Period Debit ck0001087711:PerformanceAwardsSharesDeferred
2414 Total discretionary bonus Concept (Monetary) For Period Debit ck0001087711:PerformanceAwards
2415 1190 - Disclosure - Operating Expenses Before Credit Impairment Losses, Provisions and Charges - Additional Information (Detail) Network

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2416 Disclosure of sensitivity analysis for actuarial assumptions [table] Table

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2417 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2418 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2419 Santander UK plc [member] Member ck0001087711:SubsidiaryMember
2420 Disclosure of Classes of employee benefits expense [line items] LineItems ck0001087711:DisclosureOfClassesOfEmployeeBenefitsExpenseLineItems
2421 Increase in liabilities Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseInLiabilities
2422 Average number of full-time equivalent staff Concept (Decimal) For Period ifrs-full:AverageNumberOfEmployees
2423 Impairment charge Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsOtherThanGoodwill
2424 1191 - Disclosure - Audit and Other Services - Summary of Audit and Other Services (Detail) Network

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2425 Implied Table Table

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2426 Disclosure of finance income costs [abstract] Abstract ck0001087711:DisclosureOfFinanceIncomeCostsAbstract
2427 Audit fees: Abstract ck0001087711:AuditFeesAbstract
2428 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 ck0001087711:AuditorsRemunerationForAuditServicesGroupAnnualAccounts
2429 - Audit of the Santander UK group's subsidiaries Concept (Monetary) For Period Debit ck0001087711:AuditorsRemunerationForAuditServicesGroupSubsidiaries
2430 Total audit fees Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForAuditServices
2431 Non-audit fees: Abstract ck0001087711:NonAuditFeesAbstract
2432 Audit-related assurance services Concept (Monetary) For Period Debit ck0001087711:AuditorsRemunerationForNonAuditServicesAuditRelatedServices
2433 Taxation compliance services Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForTaxServices
2434 Other assurance services Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForOtherServices
2435 Other non-audit services Concept (Monetary) For Period Debit ck0001087711:AuditorRemunerationForOtherNonauditServices
2436 Total non-audit fees Concept (Monetary) For Period Debit ck0001087711:AuditorsRemunerationForNonAuditServices
2437 1192 - Disclosure - Audit and Other Services - Summary of Audit and Other Services (Parenthetical) (Detail) Network

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2438 Disclosure of audit fees and non audit fees [table] Table

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2439 Products and services [axis] Axis ifrs-full:ProductsAndServicesAxis
2440 Products and services [member] Member ifrs-full:ProductsAndServicesMember
2441 Prior year audit services [member] Member ck0001087711:PriorYearAuditServicesMember
2442 Disclosure of audit fees and non audit fees [Line Items] LineItems ck0001087711:DisclosureOfAuditFeesAndNonAuditFeesLineItems
2443 Auditors fee Concept (Monetary) For Period Debit ifrs-full:AuditorsRemuneration
2444 Audit-related assurance services Concept (Monetary) For Period Debit ck0001087711:AuditorsRemunerationForNonAuditServicesAuditRelatedServices
2445 1193 - Disclosure - Audit and Other Services - Additional Information (Detail) Network

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2446 Disclosure of audit fees and non audit fees [table] Table

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ck0001087711:DisclosureOfAuditFeesAndNonAuditFeesTable
2447 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2448 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2449 Corporate and Other Borrowers [member] Member ck0001087711:CorporateAndOtherBorrowersMember
2450 Disclosure of audit fees and non audit fees [Line Items] LineItems ck0001087711:DisclosureOfAuditFeesAndNonAuditFeesLineItems
2451 Audit-related services related to services performed in connection with the statutory and regulatory filings Concept (Monetary) For Period Debit ck0001087711:AuditorsRemunerationForNonAuditServicesAuditRelatedServicesStatutoryAndRegulatoryFilings
2452 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 ck0001087711:AuditorsRemunerationForNonAuditServicesAuditRelatedServicesSecuritisationDebtIssuanceAndRelatedWorkAndReportingToPrudentialAndConductRegulators
2453 Audit fees payable for statutory audit Concept (Monetary) For Period Debit ifrs-full:AuditorsRemunerationForAuditServices
2454 1194 - Disclosure - Credit Impairment Losses and Provisions - Summary of Impairment Losses and Provisions (Detail) Network

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2455 Implied Table Table

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2456 Disclosure of credit impairment loss and provisions [abstract] Abstract ck0001087711:DisclosureOfCreditImpairmentLossAndProvisionsAbstract
2457 Loans and advances to customers (See Note 14) Concept (Monetary) For Period Debit ck0001087711:CreditImpairmentLossesOnLoansAndAdvancesToCustomer
2458 Recoveries of loans and advances, net of collection costs (See Note 14) Concept (Monetary) For Period Debit ck0001087711:FinancialAssetsPostWriteoffRecoveries
2459 Off-balance sheet exposures (See Note 30) Concept (Monetary) For Period Debit ck0001087711:OffBalanceSheetCreditExposures
2460 Impairment loss on financial assets Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossOnFinancialAssets
2461 Provisions for other liabilities and charges (excluding off-balance sheet credit exposures) (See Note 30) Concept (Monetary) For Period Credit ck0001087711:ProvisionsForOtherLiabilitiesAndChargesExcludingOffBalanceSheetCreditExposures
2462 Provisions for RV and voluntary termination (See Note 14) Concept (Monetary) For Period Debit ck0001087711:ProvisionsForResidualValueAndVoluntaryTermination
2463 Provisions for other liabilities and charges Concept (Monetary) For Period Debit ck0001087711:ProvisionsForOtherLiabilitiesAndCharges
2464 Total operating impairment losses, provisions and charges Concept (Monetary) For Period Debit ck0001087711:AggregateOperatingCreditImpairmentLossesProvisionsAndCharges
2465 1195 - Disclosure - Credit Impairment Losses and Provisions - Additional Information (Detail) Network

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2466 Implied Table Table

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2467 Disclosure of credit impairment loss and provisions [abstract] Abstract ck0001087711:DisclosureOfCreditImpairmentLossAndProvisionsAbstract
2468 Impairment losses on loans and advances to banks Concept (Monetary) For Period Debit ck0001087711:CreditImpairmentLossesOnLoansAndAdvancesToBank
2469 Impairment losses on Non-trading reverse repurchase agreements Concept (Monetary) For Period Debit ck0001087711:CreditImpairmentLossesOnNontradingReverseRepurchaseAgreements
2470 Impairment losses on other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001087711:CreditImpairmentLossesOnOtherFinancialAssetsAtAmortisedCost
2471 Impairment losses on financial assets at FVOCI Concept (Monetary) For Period Debit ck0001087711:CreditImpairmentLossesOnFinancialAssetsAtFVOCI
2472 1196 - Disclosure - Taxation - Disclosure of Tax on Profit (Detail) Network

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2473 Implied Table Table

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2474 Major components of tax expense (income) [abstract] Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
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2476 UK corporation tax on profit for the year Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncome
2477 Adjustments in respect of prior years Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForCurrentTaxOfPriorPeriod
2478 Total current tax Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriods
2479 Deferred tax: Abstract ifrs-full:DeferredTaxExpenseIncomeAbstract
2480 Charge/(credit) for the year Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncomeRelatingToOriginationAndReversalOfTemporaryDifferences
2481 Adjustments in respect of prior years Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDeferredTaxOfPriorPeriods
2482 Total deferred tax Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncome
2483 Tax on profit Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2484 1197 - Disclosure - Taxation - Additional Information (Detail) Network

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2485 Income Tax Expense Benefits [table] Table

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2487 Non-adjusting Events After Reporting Period [member] Member ifrs-full:NonadjustingEventsMember
2488 Finance (No.2) Act 2015 [member] Member ck0001087711:FinanceAct2015Member
2489 Finance (No.2) Act 2016 [member] Member ck0001087711:FinanceAct2016Member
2490 Range [axis] Axis ifrs-full:RangeAxis
2491 Ranges [member] Member ifrs-full:RangesMember
2492 Top of Range [member] Member ifrs-full:TopOfRangeMember
2493 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
2494 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2495 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2496 Santandar UK plc [member] Member ck0001087711:CompanyMember
2497 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
2498 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
2499 Banking Entities [member] Member ck0001087711:BankingEntitiesMember
2500 Non-banking Entities [member] Member ck0001087711:NonBankingEntitiesMember
2501 Corporation Tax Rate in 2020 [member] Member ck0001087711:CorporationTaxRateIn2020Member
2502 Deferred Tax Assets That Rely on Future Profitability Excluding Timing Differences [member] Member ck0001087711:DeferredTaxAssetMember
2503 Income Tax Expense Benefits [line items] LineItems ck0001087711:IncomeTaxExpenseBenefitsLineItems
2504 Applicable tax rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
2505 Bank corporation tax surcharge Concept (Percent) For Period ck0001087711:BankCorporationTaxSurcharge
2506 Effective tax rate Concept (Percent) For Period ifrs-full:AverageEffectiveTaxRate
2507 Recognised capital losses carried forward Concept (Monetary) For Period Debit ck0001087711:RecognisedUKCapitalLossesCarriedForward
2508 Unrecognised capital losses carried forward Concept (Monetary) For Period Debit ck0001087711:UnrecognisedCapitalLossesCarriedForward
2509 Net operating losses carried forward Concept (Monetary) For Period Debit ck0001087711:NetUSOperatingLossesCarriedForward
2510 1198 - Disclosure - Taxation - Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate (Detail) Network

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2511 Implied Table Table

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2512 Reconciliation of accounting profit multiplied by applicable tax rates [abstract] Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
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2514 Tax calculated at a tax rate of 19% (2017: 19.25%, 2016: 20.00%) Concept (Monetary) For Period Debit ifrs-full:TaxExpenseIncomeAtApplicableTaxRate
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2516 Non-deductible preference dividends paid Concept (Monetary) For Period Debit ck0001087711:TaxEffectOfNonDeductiblePreferenceDividendsPaid
2517 Non-deductible UK Bank Levy Concept (Monetary) For Period Debit ck0001087711:TaxEffectOfNonDeductibleBankLevy
2518 Non-deductible conduct remediation, fines and penalties Concept (Monetary) For Period Debit ck0001087711:TaxEffectOfNonDeductibleConductRemediationFinesAndPenalties
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2520 Effect of change in tax rate on deferred tax provision Concept (Monetary) For Period Debit ifrs-full:TaxEffectFromChangeInTaxRate
2521 Adjustment to prior year provisions Concept (Monetary) For Period Debit ck0001087711:TaxEffectOfPriorYearAdjustments
2522 Tax charge Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2523 1199 - Disclosure - Taxation - Schedule of Tax on Profit Before Tax Differs from Theoretical Amount that Arise Using Basic Corporation Tax Rate (Parenthetical) (Detail) Network

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2524 Implied Table Table

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2525 Reconciliation of accounting profit multiplied by applicable tax rates [abstract] Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
2526 Standard tax rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
2527 1200 - Disclosure - Taxation - Disclosure of Movements in Current Tax Assets and Liabilities (Detail) Network

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2528 Implied Table Table

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2529 Current Tax Assets and Liabilities [abstract] Abstract ck0001087711:CurrentTaxAssetsAndLiabilitiesAbstract
2530 Assets Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssets
2531 Liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilities
2532 Beginning Balance Concept (Monetary) As Of Credit ck0001087711:CurrentTaxLiabilityAsset
2533 Income statement charge Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncomeAndAdjustmentsForCurrentTaxOfPriorPeriods
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2535 Corporate income tax paid Concept (Monetary) For Period Credit ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities
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2537 Ending Balance Concept (Monetary) As Of Credit ck0001087711:CurrentTaxLiabilityAsset
2538 Assets Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssets
2539 Liabilities Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilities
2540 1201 - Disclosure - Taxation - Disclosure of Deferred Tax Assets and Liabilities Including Movement in Deferred Tax Account (Detail) Network

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2541 Disclosure of temporary difference, unused tax losses and unused tax credits [table] Table

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2544 Fair Value of Financial Instruments [member] Member ck0001087711:FairValueOfFinancialInstrumentsMember
2545 Pension Remeasurement [member] Member ck0001087711:PensionRemeasurementMember
2546 Cash Flow Hedges [member] Member ifrs-full:CashFlowHedgesMember
2547 Available-for-Sale [member] Member ck0001087711:AvailableForSaleMember
2548 Fair Value Reserves Related to Gains or Losses on Cash Flow Hedges [Member] Member ck0001087711:FairValueReserveMember
2549 Tax Losses Carried Forward [member] Member ifrs-full:UnusedTaxLossesMember
2550 Accelerated Tax Depreciation [member] Member ck0001087711:AcceleratedTaxDepreciationMember
2551 Other temporary differences [member] Member ifrs-full:OtherTemporaryDifferencesMember
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2555 Beginning Balance, After adoption of IFRS 9 Concept (Monetary) As Of Credit ck0001087711:DeferredTaxLiabilityAssetAfterAdoptionOfIfrs9
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2560 1202 - Disclosure - Dividends on Ordinary Shares - Disclosure of Dividends on Ordinary Shares Declared and Paid (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureDividendsOnOrdinarySharesAdditionalInformation
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2576 1204 - Disclosure - Trading Assets - Disclosure of Trading Assets (Detail) Network

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2587 1205 - Disclosure - Derivative Financial Instruments - Notional Amounts and Fair Values of Derivatives (Detail) Network

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2588 Disclosure of detailed information about hedges [table] Table

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2620 1207 - Disclosure - Derivative Financial Instruments - Analysis of the Notional and Fair Values of Derivatives by Trading and Settlement Method (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDerivativeFinancialInstrumentsAnalysisOfTheNotionalAndFairValuesOfDerivativesByTradingAndSettlementMethod
2621 Disclosure of Analysis of Notional and Fair Values of Derivatives by Trading and Settlement Method [table] Table

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2637 1208 - Disclosure - Derivative Financial Instruments - Summary of Fixed Rate Instruments Hedged (Detail) Network

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2638 Disclosure of detailed information about hedged items [table] Table

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2648 Currency Concept (Text/String) For Period ck0001087711:UnderlyingCurrency
2649 1209 - Disclosure - Derivative Financial Instruments - Summary of Maturity Profile and Average Price/Rate of Hedging Instruments Used in Hedging Strategies (Detail) Network

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2682 1210 - 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

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2683 Disclosure of detailed information about hedges [table] Table

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2692 Hedge ineffectiveness Concept (Monetary) For Period Credit ifrs-full:GainLossOnHedgeIneffectiveness
2693 1211 - Disclosure - Derivative Financial Instruments - Summary of Information About Hedging Ineffectiveness by Risk Category (Detail) Network

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2694 Disclosure of detailed information about hedges [table] Table

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2711 Amount reclassified from cash flow hedging reserve to income statement Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesForWhichHedgedItemAffectedProfitOrLossNetOfTax
2712 1212 - Disclosure - Derivative Financial Instruments - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDerivativeFinancialInstrumentsAdditionalInformation
2713 Implied Table Table

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2716 1213 - 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

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2717 Disclosure of detailed information about hedges [table] Table

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2729 1214 - Disclosure - Derivative Financial Instruments - Summary of Details of Hedged Exposures by Hedging Strategies (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDerivativeFinancialInstrumentsSummaryOfDetailsOfHedgedExposuresByHedgingStrategies
2730 Disclosure of detailed information about hedges [table] Table

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2771 1215 - 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

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2784 1216 - 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

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2792 1217 - Disclosure - Other Financial Assets at Fair Value Through Profit or Loss - Additional Information (Detail) Network

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2796 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
2797 Disclosure of other financial assets at fair value through profit or loss [Line Items] LineItems ck0001087711:DisclosureOfOtherFinancialAssetsAtFairValueThroughProfitOrLossLineItems
2798 Financial assets mandatorily at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
2799 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
2800 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
2801 1218 - Disclosure - Loans and Advances to Customers - Summary of Net Loans and Advances to Customers (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureLoansAndAdvancesToCustomersSummaryOfNetLoansAndAdvancesToCustomers
2802 Implied Table Table

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*

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2803 Net Loans and Advances to Customers [abstract] Abstract ck0001087711:NetLoansAndAdvancesToCustomersAbstract
2804 Loans secured on residential properties Concept (Monetary) As Of Debit ck0001087711:LoansSecuredOnResidentialProperties
2805 Corporate loans Concept (Monetary) As Of Debit ifrs-full:CorporateLoans
2806 Finance leases Concept (Monetary) As Of Debit ifrs-full:FinanceLeaseReceivables
2807 Other unsecured loans Concept (Monetary) As Of Debit ck0001087711:OtherUnsecuredLoans
2808 Amounts due from fellow Banco Santander subsidiaries and joint ventures Concept (Monetary) As Of Debit ifrs-full:TradeAndOtherReceivablesDueFromRelatedParties
2809 Amounts due from Santander UK Group Holdings plc Concept (Monetary) As Of Debit ifrs-full:TradeAndOtherReceivables
2810 Loans and advances to customers Concept (Monetary) As Of Debit ck0001087711:LoansAndAdvancesToCustomersGross
2811 Credit impairment loss allowances on loans and advances to customers Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
2812 RV and voluntary termination provisions on finance leases Concept (Monetary) As Of Credit ck0001087711:ResidualValueAndVoluntaryTerminationProvisions
2813 Net loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
2814 1219 - Disclosure - Loans and Advances to Customers - Summary of Movement in Impairment Loss Allowances (Detail) Network

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2815 Movement in impairment loss allowances for loan and advances to customers [table] Table

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ck0001087711:MovementInImpairmentLossAllowancesForLoanAndAdvancesToCustomersTable
2816 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
2817 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
2818 Advances secured on residential property [member] Member ck0001087711:AdvancesSecuredOnResidentialPropertyMember
2819 Corporate loans [member] Member ifrs-full:CorporateLoansMember
2820 Finance leases [member] Member ifrs-full:LeaseReceivablesMember
2821 Other unsecured advances [member] Member ck0001087711:OtherUnsecuredLoansMember
2822 Movement in impairment loss allowances for loan and advances to customers [line items] LineItems ck0001087711:MovementInImpairmentLossAllowancesForLoanAndAdvancesToCustomersLineItems
2823 Beginning balance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
2824 Adoption of IFRS 9 (see Note 1) Concept (Monetary) For Period Debit ck0001087711:AdjustmentForAdoptionOfIFRS9AllowanceAccountForCreditLossesOfFinancialAssets
2825 Re-allocation of ECL on off-balance sheet exposures Concept (Monetary) For Period Debit ck0001087711:ReallocationOfExpectedCreditLossOnUndrawnExposures
2826 Balance at 1 January 2018 Concept (Monetary) As Of Credit ck0001087711:AllowanceAccountForCreditLossesOfFinancialAssetOnAdoptionOfIFRS9
2827 (Release)/charge to the income statement (see Note 8) Concept (Monetary) For Period Debit ck0001087711:ImpairmentLossesOnLoansAndAdvancesToCustomer
2828 Write-offs and other items Concept (Monetary) For Period Debit ifrs-full:UtilisationAllowanceAccountForCreditLossesOfFinancialAssets
2829 Ending balance Concept (Monetary) As Of Credit ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
2830 Observed Concept (Monetary) As Of Credit ck0001087711:ImpairmentAllowancesAgainstLoansAndAdvancesCustomersObserved
2831 Incurred but not yet observed Concept (Monetary) As Of Debit ck0001087711:ImpairmentAllowancesIncurredButNotYetObserved
2832 Recoveries, net of collection costs (see Note 8) Concept (Monetary) For Period ifrs-full:ReversalAllowanceAccountForCreditLossesOfFinancialAssets
2833 1220 - Disclosure - Loans and Advances to Customers - Summary of Movement in Impairment Loss Allowances (Parenthetical) (Detail) Network

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2834 Implied Table Table

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2835 Disclosure of impairment loss recognised or reversed for cash-generating unit [abstract] Abstract ifrs-full:DisclosureOfImpairmentLossRecognisedOrReversedAbstract
2836 Mortgage write-offs of financial assets Concept (Monetary) For Period Debit ck0001087711:MortgageWriteoffsIncludingEffectOfDiscounting
2837 Contractual amount outstanding on financial assets, written off Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsWrittenOffDuringReportingPeriodAndStillSubjectToEnforcementActivityContractualAmountOutstanding
2838 1221 - Disclosure - Loans and Advances to Customers - Summary of Finance Lease and Hire Purchase Contract Receivables (Detail) Network

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2839 Disclosure of finance costs and unwinding of obligations [table] Table

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*

ck0001087711:DisclosureOfFinanceCostsAndUnwindingOfObligationsTable
2840 Maturity [axis] Axis ifrs-full:MaturityAxis
2841 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
2842 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
2843 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
2844 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
2845 Disclosure of finance lease and hire purchase contract receivables [line items] LineItems ck0001087711:DisclosureOfFinanceLeaseAndHirePurchaseContractReceivablesLineItems
2846 Gross investment Concept (Monetary) As Of Debit ifrs-full:GrossInvestmentInFinanceLease
2847 Unearned finance income Concept (Monetary) As Of Debit ifrs-full:UnearnedFinanceIncomeOnFinanceLease
2848 Net investment Concept (Monetary) As Of Debit ifrs-full:NetInvestmentInFinanceLease
2849 1222 - Disclosure - Loans and Advances To Customers - Additional Information (Detail) Network

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*

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2850 Implied Table Table

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2851 Disclosure of finance lease and hire purchase contract receivables [abstract] Abstract ck0001087711:DisclosureOfFinanceLeaseAndHirePurchaseContractReceivablesAbstract
2852 Unguaranteed residual value of leases Concept (Monetary) As Of Debit ifrs-full:DiscountedUnguaranteedResidualValueOfAssetsSubjectToFinanceLease
2853 Contingent rent income Concept (Monetary) As Of Credit ck0001087711:ContingentRentIncome
2854 1223 - Disclosure - Securitisations and Covered Bonds - Analysis of Securitisations and Covered Bonds (Detail) Network

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2855 Disclosure of securitisations and covered bonds [table] Table

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ck0001087711:DisclosureOfSecuritisationsAndCoveredBondsTable
2856 Securitisation By Company Name [axis] Axis ck0001087711:SecuritisationByCompanyNameAxis
2857 Securitisation By Company Name [domain] Member ck0001087711:SecuritisationByCompanyNameDomain
2858 Holmes [member] Member ck0001087711:HolmesMember
2859 Fosse [member] Member ck0001087711:FosseMember
2860 Langton [member] Member ck0001087711:LangtonMember
2861 Auto ABS UK Loans [member] Member ck0001087711:AutoABSUKLoansMember
2862 Euro 35bn Global Covered Bond Programme [member] Member ck0001087711:EuroThirtyFiveBillionGlobalCoveredBondProgrammeMember
2863 Motor [member] Member ck0001087711:MotorMember
2864 Securitization By Program Name [axis] Axis ck0001087711:SecuritizationByProgramNameAxis
2865 Securitization By Program Name [domain] Member ck0001087711:SecuritizationByProgramNameDomain
2866 Covered Bond Programme [member] Member ck0001087711:CoveredBondProgrammeMember
2867 Securitisation Programmes [member] Member ck0001087711:SecuritisationProgrammesMember
2868 Type Of Securitisation [axis] Axis ck0001087711:TypeOfSecuritisationAxis
2869 Type Of Securitisation [domain] Member ck0001087711:TypeOfSecuritisationDomain
2870 Master Trust Structures [member] Member ck0001087711:MasterTrustStructuresMember
2871 Other Securitisation Structures [member] Member ck0001087711:OtherSecuritisationStructuresMember
2872 Disclosure of securitisations and covered bonds [line items] LineItems ck0001087711:DisclosureOfSecuritisationsAndCoveredBondsLineItems
2873 Gross assets Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedInEntitysFinancialStatementsInRelationToStructuredEntities
2874 External notes in issue Concept (Monetary) As Of Credit ifrs-full:NotesAndDebenturesIssued
2875 Notes issued to Santander UK plc/subsidiaries as collateral Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
2876 held by the Santander UK group Concept (Monetary) As Of Credit ck0001087711:NotesInIssueHeldByGroup
2877 Total securitisation and covered bond programmes (see Note 28) Concept (Monetary) As Of Credit ck0001087711:SecuritisationsAndCoveredBond
2878 1224 - Disclosure - Securitisations and Covered Bonds - Summary of Issuances and Redemptions of Securitisation and Covered Bond Programme (Detail) Network

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2879 Issuances And Redemptions Of Securitisation And Covered Bond [table] Table

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ck0001087711:IssuancesAndRedemptionsOfSecuritisationAndCoveredBondTable
2880 Securitization By Program Name [axis] Axis ck0001087711:SecuritizationByProgramNameAxis
2881 Securitization By Program Name [domain] Member ck0001087711:SecuritizationByProgramNameDomain
2882 Internal [member] Member ck0001087711:InternalMember
2883 External [member] Member ck0001087711:ExternalMember
2884 Type Of Securitisation [axis] Axis ck0001087711:TypeOfSecuritisationAxis
2885 Type Of Securitisation [domain] Member ck0001087711:TypeOfSecuritisationDomain
2886 Master Trust Structures [member] Member ck0001087711:MasterTrustStructuresMember
2887 Other Securitisation Structures [member] Member ck0001087711:OtherSecuritisationStructuresMember
2888 Covered Bond Programme [member] Member ck0001087711:CoveredBondProgrammeMember
2889 Securitisation By Company Name [axis] Axis ck0001087711:SecuritisationByCompanyNameAxis
2890 Securitisation By Company Name [domain] Member ck0001087711:SecuritisationByCompanyNameDomain
2891 Holmes [member] Member ck0001087711:HolmesMember
2892 Fosse [member] Member ck0001087711:FosseMember
2893 Motor [member] Member ck0001087711:MotorMember
2894 Auto ABS UK Loans [member] Member ck0001087711:AutoABSUKLoansMember
2895 Issuances And Redemptions Of Securitisation And Covered Bond [Line items] LineItems ck0001087711:IssuancesAndRedemptionsOfSecuritisationAndCoveredBondLineItems
2896 Internal and external issuances Concept (Monetary) For Period Credit ck0001087711:MortgageBackedNotesIssued
2897 Internal and external redemptions Concept (Monetary) For Period Debit ck0001087711:MortgageBackedSecuritiesRedeemed
2898 1225 - Disclosure - Securitisations and Covered Bonds - Additional Information (Detail) Network

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2899 Gross assets securitised [table] Table

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ck0001087711:GrossAssetsSecuritisedTable
2900 Securitisation By Company Name [axis] Axis ck0001087711:SecuritisationByCompanyNameAxis
2901 Securitisation By Company Name [domain] Member ck0001087711:SecuritisationByCompanyNameDomain
2902 Holmes [member] Member ck0001087711:HolmesMember
2903 Fosse [member] Member ck0001087711:FosseMember
2904 Langton [member] Member ck0001087711:LangtonMember
2905 Disclosure of gross asset securitised [line items] LineItems ck0001087711:DisclosureOfGrossAssetSecuritisedLineItems
2906 Beneficial interest in residential mortgage loans Concept (Monetary) As Of Debit ck0001087711:BeneficialInterestInMortgages
2907 Cash deposits Concept (Monetary) As Of Credit ck0001087711:CashDeposit
2908 1226 - 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

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2909 Disclosure of continuing involvement in derecognised financial assets [table] Table

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ifrs-full:DisclosureOfContinuingInvolvementInDerecognisedFinancialAssetsTable
2910 Continuing involvement in derecognised financial assets by type of transfer [axis] Axis ifrs-full:ContinuingInvolvementInDerecognisedFinancialAssetsByTypeOfTransferAxis
2911 Types of transfer [member] Member ifrs-full:TypesOfTransferMember
2912 Sale and Repurchase Agreements [member] Member ck0001087711:SaleAndRepurchaseAgreementsMember
2913 Securities lending agreements [member] Member ck0001087711:SecuritiesLendingAgreementsMember
2914 Securitisations [member] Member ifrs-full:SecuritisationsMember
2915 Disclosure of continuing involvement in derecognised financial assets [line items] LineItems ifrs-full:DisclosureOfContinuingInvolvementInDerecognisedFinancialAssetsLineItems
2916 Carrying amount of financial assets not derecognised in their entirety Concept (Monetary) As Of Debit ifrs-full:RecognisedAssetsRepresentingContinuingInvolvementInDerecognisedFinancialAssets
2917 Carrying amount of associated financial liabilities Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesRepresentingContinuingInvolvementInDerecognisedFinancialAssets
2918 1227 - Disclosure - Reverse Repurchase Agreements - Non Trading - Summary of Reverse Repurchase Agreements - Non Trading (Detail) Network

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2919 Disclosure of reserve repurchase agreements non-trading [table] Table

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ck0001087711:DisclosureOfReserveRepurchaseAgreementsNontradingTable
2920 Types of agreement [axis] Axis ck0001087711:TypesOfAgreementAxis
2921 Types of agreement [domain] Member ck0001087711:TypesOfAgreementDomain
2922 Agreements with banks [member] Member ck0001087711:AgreementsWithBanksMember
2923 Agreements with customers [member] Member ck0001087711:AgreementsWithCustomersMember
2924 Disclosure of reserve repurchase agreements non-trading [line items] LineItems ck0001087711:DisclosureOfReserveRepurchaseAgreementsNontradingLineItems
2925 Reverse repurchase agreements-non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
2926 1228 - Disclosure - Other Financial Assets At Amortised Cost - Summary of Other Financial Assets at Amortised Cost (Detail) Network

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2927 Financial Assets At Fair Value Through Profit Or Loss [table] Table

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ck0001087711:FinancialAssetsAtFairValueThroughProfitOrLossTable
2928 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
2929 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
2930 Other Financial Assets [member] Member ck0001087711:OtherFinancialAssets1Member
2931 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
2932 Assets [member] Member ifrs-full:ClassesOfAssetsMember
2933 Asset backed securities [member] Member ck0001087711:AssetBackedSecuritiesMember
2934 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
2935 Financial assets at amortised cost [line items] LineItems ck0001087711:OtherFinancialAssetsAtAmortisedCostLineItems
2936 Financial assets at amortised cost Concept (Monetary) As Of Debit ck0001087711:OtherFinancialAssetsAtAmortisedCost
2937 1229 - Disclosure - Financial Assets At Fair Value Through Other Comprehensive Income - Summary of Financial Assets at Fair Value Through Other Comprehensive Income (Detail) Network

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2938 Implied Table Table

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2939 Financial assets at fair value through other comprehensive income [abstract] Abstract ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeAbstract
2940 Debt securities Concept (Monetary) As Of Debit ck0001087711:DebtSecuritiesClassifiedAsFairValueThroughOtherComprehensiveIncome
2941 Loans and advances to customers Concept (Monetary) As Of Debit ck0001087711:LoansAndAdvanceToCustomersClassifiedAsFairValueThroughOtherComprehensiveIncome
2942 Financial assets at fair value through other comprehensive income Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
2943 1230 - Disclosure - Financial Investments - Summary of Financial Investments (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInvestmentsSummaryOfFinancialInvestments
2944 Disclosure of financial investments [table] Table

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ck0001087711:DisclosureOfFinancialInvestmentsTable
2945 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
2946 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
2947 Available-for-sale [member] Member ifrs-full:FinancialAssetsAvailableforsaleCategoryMember
2948 Held-to-maturity debt securities [member] Member ifrs-full:HeldtomaturityInvestmentsCategoryMember
2949 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
2950 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
2951 Asset-backed Securities [member] Member ck0001087711:AssetBackedSecuritiesAssetsMember
2952 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
2953 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
2954 Disclosure of financial investments [line items] LineItems ck0001087711:DisclosureOfFinancialInvestmentsLineItems
2955 Financial investments Concept (Monetary) As Of Debit ck0001087711:FinancialInvestments
2956 1231 - Disclosure - Interests in Other Entities - Schedule of Interests in Other Entities (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureInterestsInOtherEntitiesScheduleOfInterestsInOtherEntities
2957 Implied Table Table

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2958 Disclosure of interest in other entities [abstract] Abstract ck0001087711:DisclosureOfInterestInOtherEntitiesAbstract
2959 Joint ventures Concept (Monetary) As Of Debit ifrs-full:InvestmentsInJointVentures
2960 Total Concept (Monetary) As Of Debit ifrs-full:InvestmentsInSubsidiariesJointVenturesAndAssociates
2961 1232 - Disclosure - Interests In Other Entities - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureInterestsInOtherEntitiesAdditionalInformation
2962 Disclosure of subsidiaries [table] Table

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*

ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
2963 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
2964 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
2965 Santander UK Operations Ltd [member] Member ck0001087711:SantanderUkOperationsLtdMember
2966 Santander UK Technology Ltd [member] Member ck0001087711:SantanderUkTechnologyLtdMember
2967 Produban servicios informaticos generales SI [member] Member ck0001087711:ProdubanServiciosInformaticosGeneralesSlMember
2968 Santander Equity Investments Limited [member] Member ck0001087711:SantanderEquityInvestmentsLimitedMember
2969 Santander UK Group Holdings plc [member] Member ck0001087711:SantanderUkGroupHoldingsPlcMember
2970 ANTS plc [member] Member ck0001087711:ANTSPlcMember
2971 Jersey and Isle of Man branches [member] Member ck0001087711:JerseyAndIsleOfManBranchesMember
2972 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2973 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2974 Subsidiaries with material non-controlling interests [member] Member ifrs-full:SubsidiariesWithMaterialNoncontrollingInterestsMember
2975 Non-adjusting events after reporting period [axis] Axis ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
2976 Non-adjusting Events After Reporting Period [member] Member ifrs-full:NonadjustingEventsMember
2977 Events After Reporting Period [member] Member ck0001087711:EventsAfterReportingPeriodMember
2978 Disclosure of subsidiaries [line items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
2979 Percentage of ownership in subsidiaries Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInSubsidiary
2980 Cash consideration Concept (Monetary) For Period Credit ifrs-full:ConsiderationPaidReceived
2981 Aggregate net asset on acquisition date Concept (Monetary) As Of Debit ifrs-full:IdentifiableAssetsAcquiredLiabilitiesAssumed
2982 Percentage of sale of share capital in subsidiaries Concept (Percent) For Period ck0001087711:SaleOfShareCapitalIssuedPercentage
2983 Dividends on transfer of share capital Concept (Monetary) For Period Debit ifrs-full:DividendsPaidOrdinaryShares
2984 Increase (decrease) in investment property Concept (Monetary) For Period Debit ifrs-full:ChangesInInvestmentProperty
2985 Disposals, investment property Concept (Monetary) For Period Credit ifrs-full:DisposalsInvestmentProperty
2986 1233 - Disclosure - Interests in Other Entities - Schedule of Subsidiaries With Significant Non-Controlling Interests (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureInterestsInOtherEntitiesScheduleOfSubsidiariesWithSignificantNonControllingInterests
2987 Disclosure of subsidiaries [table] Table

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*

ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
2988 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
2989 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
2990 Subsidiaries with material non-controlling interests [member] Member ifrs-full:SubsidiariesWithMaterialNoncontrollingInterestsMember
2991 Disclosure of subsidiaries [line items] LineItems ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
2992 Profit attributable to non-controlling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
2993 Accumulated non-controlling interests of the subsidiary Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
2994 Dividends paid to non-controlling interests Concept (Monetary) For Period Credit ifrs-full:DividendsPaidToNoncontrollingInterests
2995 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
2996 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
2997 Profit for the year Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
2998 Total comprehensive income for the year Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
2999 1234 - Disclosure - Interests In Other Entities - Interests in Joint Ventures - Additional Information (Detail) Network

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3000 Disclosure of information about unconsolidated subsidiaries [table] Table

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*

ifrs-full:DisclosureOfInformationAboutUnconsolidatedSubsidiariesTable
3001 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
3002 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
3003 Joint ventures [member] Member ifrs-full:JointVenturesMember
3004 Disclosure of joint ventures [line items] LineItems ifrs-full:DisclosureOfJointVenturesLineItems
3005 Profit after tax Concept (Monetary) For Period Credit ifrs-full:ShareOfProfitLossOfContinuingOperationsOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
3006 Carrying value of interest in joint venture Concept (Monetary) As Of Debit ifrs-full:InvestmentsInJointVentures
3007 Commitments and contingent liabilities Concept (Monetary) As Of Credit ck0001087711:CommitmentsAndContingencies1
3008 1235 - Disclosure - Interests In Other Entities - Interests in Unconsolidated Structured Entities - Additional Information (Detail) Network

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3009 Disclosure of information about unconsolidated subsidiaries [table] Table

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*

ifrs-full:DisclosureOfInformationAboutUnconsolidatedSubsidiariesTable
3010 Unconsolidated structured entities [axis] Axis ifrs-full:UnconsolidatedStructuredEntitiesAxis
3011 Entity's total for unconsolidated structured entities [member] Member ifrs-full:EntitysTotalForUnconsolidatedStructuredEntitiesMember
3012 Santander (UK) Common Investment Fund [member] Member ck0001087711:SantanderUkCommonInvestmentFundMember
3013 Abbey National Capital Trust I [member] Member ck0001087711:AbbeyNationalCapitalTrustiMember
3014 Abbey National Capital LP I [member] Member ck0001087711:AbbeyNationalCapitalLpMember
3015 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3016 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3017 Entities with Joint Control or Significant Influence over Entity [Member] Member ifrs-full:JointControlOrSignificantInfluenceMember
3018 Disclosure of information about unconsolidated subsidiaries [line items] LineItems ifrs-full:DisclosureOfInformationAboutUnconsolidatedSubsidiariesLineItems
3019 Defined benefit assets and obligations Concept (Monetary) As Of Debit ifrs-full:AssetsOfBenefitPlan
3020 Name of subsidiary Concept (Text/String) For Period ifrs-full:NameOfSubsidiary
3021 Ownership interest in trust preferred entities by Santander UK plc Concept (Percent) For Period ifrs-full:ProportionOfOwnershipInterestInSubsidiary
3022 Non-cumulative trust preferred securities issued Concept (Monetary) For Period Credit ck0001087711:NoncumulativeTrustPreferredSecuritiesIssued
3023 Non-cumulative trust preferred securities interest rate Concept (Percent) For Period ck0001087711:NoncumulativeTrustPreferredSecuritiesInterestRate
3024 Number of credit protection vehicles Concept (Decimal) For Period ck0001087711:NumberOfCreditProtectionVehicles
3025 Credit Linked Notes issued Concept (Monetary) As Of Credit ck0001087711:CreditLinkedNotesIssued
3026 1236 - Disclosure - Intangible Assets - Schedule of Goodwill (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureIntangibleAssetsScheduleOfGoodwill
3027 Disclosure of Goodwill [table] Table

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ck0001087711:DisclosureOfGoodwillTable
3028 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
3029 Carrying amount [member] Member ifrs-full:CarryingAmountMember
3030 Cost [member] Member ifrs-full:GrossCarryingAmountMember
3031 Accumulated Impairment [member] Member ifrs-full:AccumulatedImpairmentMember
3032 Disclosure of goodwill [line items] LineItems ck0001087711:DisclosureOfGoodwillLineItems
3033 Carrying amount Concept (Monetary) As Of Debit ifrs-full:Goodwill
3034 1237 - Disclosure - Intangible Assets - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureIntangibleAssetsAdditionalInformation
3035 Implied Table Table

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implied:Table
3036 Disclosure of detailed information about intangible assets [abstract] Abstract ifrs-full:DisclosureOfIntangibleAssetsAbstract
3037 Goodwill impairment recognised Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossGoodwill
3038 Increase/(decrease) in discount rate percentage Concept (Percent) For Period ck0001087711:IncreaseDecreaseInDiscountRateAppliedToCashFlowProjections
3039 Discount rate percentage Concept (Percent) As Of ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
3040 1238 - Disclosure - Intangible Assets - Schedule of Goodwill for Cash Generating Units (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureIntangibleAssetsScheduleOfGoodwillForCashGeneratingUnits
3041 Disclosure of information for cash-generating units [table] Table

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ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesTable
3042 Individual assets or cash-generating units [axis] Axis ifrs-full:IndividualAssetsOrCashgeneratingUnitsAxis
3043 Entity's total for individual assets or cash-generating units [member] Member ifrs-full:EntitysTotalForIndividualAssetsOrCashgeneratingUnitsMember
3044 Personal Financial Services [member] Member ck0001087711:PersonalFinancialServicesMember
3045 Private Banking [member] Member ck0001087711:PrivateBankingMember
3046 Other [member] Member ck0001087711:OtherMember
3047 Disclosure of information for cash-generating units [line items] LineItems ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesLineItems
3048 Goodwill Concept (Monetary) As Of Debit ifrs-full:Goodwill
3049 Discount rate Concept (Percent) As Of ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
3050 Growth rate Concept (Percent) As Of ifrs-full:DescriptionOfGrowthRateUsedToExtrapolateCashFlowProjections
3051 1239 - Disclosure - Intangible Assets - Schedule of Goodwill for Cash Generating Units (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureIntangibleAssetsScheduleOfGoodwillForCashGeneratingUnitsParenthetical
3052 Implied Table Table

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implied:Table
3053 Disclosure of information for cash-generating units [abstract] Abstract ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAbstract
3054 Terminal growth rate Concept (Percent) For Period ck0001087711:TerminalGrowthRateUsedToExtrapolateCashFlowProjections
3055 1240 - Disclosure - Intangible Assets - Schedule of Other Intangibles (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureIntangibleAssetsScheduleOfOtherIntangibles
3056 Disclosure of detailed information about intangible assets [table] Table

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ifrs-full:DisclosureOfIntangibleAssetsTable
3057 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
3058 Carrying amount [member] Member ifrs-full:CarryingAmountMember
3059 Cost [member] Member ifrs-full:GrossCarryingAmountMember
3060 Accumulated Amortisation / Impairment [member] Member ifrs-full:AccumulatedDepreciationAmortisationAndImpairmentMember
3061 Disclosure of detailed information about intangible assets [line items] LineItems ifrs-full:DisclosureOfIntangibleAssetsLineItems
3062 Beginning balance Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
3063 Additions Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
3064 Write offs Concept (Monetary) For Period Credit ifrs-full:RetirementsIntangibleAssetsOtherThanGoodwill
3065 Disposals Concept (Monetary) For Period Credit ifrs-full:DisposalsIntangibleAssetsOtherThanGoodwill
3066 Charge Concept (Monetary) For Period ifrs-full:AmortisationIntangibleAssetsOtherThanGoodwill
3067 Sales Concept (Monetary) For Period Credit ck0001087711:SalesIntangibleAssetsOtherThanGoodwill
3068 Impairment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossIntangibleAssetsOtherThanGoodwill
3069 Ending balance Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
3070 1241 - Disclosure - Trading Liabilities - Schedule of Trading Liabilities (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureTradingLiabilitiesScheduleOfTradingLiabilities
3071 Disclosure of financial liabilities held for trading [table] Table

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ck0001087711:DisclosureOfFinancialLiabilitiesHeldForTradingTable
3072 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3073 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3074 Securities Sold Under Repurchase Agreements [member] Member ck0001087711:SecuritiesSoldUnderRepurchaseAgreementsMember
3075 Short Positions in Securities and Unsettled Trades [member] Member ck0001087711:ShortPositionsInSecuritiesAndUnsettledTradesMember
3076 Cash Collateral [member] Member ck0001087711:CashCollateralMember
3077 Disclosure of financial liabilities held for trading [line items] LineItems ck0001087711:DisclosureOfFinancialLiabilitiesHeldForTradingLineItems
3078 Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
3079 1242 - 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

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossSummaryOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
3080 Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [table] Table

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ck0001087711:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossTable
3081 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3082 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3083 US Dollar Ten Billion Euro commercial paper programmes [member] Member ck0001087711:UsDollarTenBillionEuroCommercialPaperProgrammesMember
3084 US$30bn Euro Medium Term Note Programme [member] Member ck0001087711:USDollarThirtyBillionEuroMediumTermNoteProgrammeMember
3085 Structured Notes Programmes [member] Member ck0001087711:StructuredNotesProgrammesMember
3086 Eurobonds [member] Member ck0001087711:EurobondsMember
3087 Structured Deposits [member] Member ck0001087711:StructuredDepositsMember
3088 Collateral and associated financial guarantees [member] Member ck0001087711:CollateralsAndGuaranteesMember
3089 Repurchase agreements - non trading [member] Member ck0001087711:RepurchaseAgreementsNontradingMember
3090 Disclosure of other financial liabilities at fair value through profit or loss [line items] LineItems ck0001087711:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossLineItems
3091 Other financial liabilities through profit or loss Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
3092 1243 - 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

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossSummaryOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossParenthetical
3093 Disclosure Of Other Financial Liabilities At Fair Value Through Profit Or Loss [table] Table

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ck0001087711:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossTable
3094 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3095 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3096 Santandar UK plc [member] Member ck0001087711:CompanyMember
3097 Disclosure of other financial liabilities at fair value through profit or loss [line items] LineItems ck0001087711:DisclosureOfOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossLineItems
3098 Financial liabilities designated at fair value through profit or loss Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossDesignatedAsUponInitialRecognition
3099 Financial liabilities mandatorily at fair value through profit or loss Concept (Monetary) As Of Credit ck0001087711:FinancialLiabilitiesMandatorilyAtFairValueThroughProfitOrLoss
3100 1244 - Disclosure - Other Financial Liabilities at Fair Value Through Profit or Loss - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureOtherFinancialLiabilitiesAtFairValueThroughProfitOrLossAdditionalInformation
3101 Implied Table Table

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implied:Table
3102 Other financial liabilities at fair value through profit or loss [abstract] Abstract ck0001087711:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLossAbstract
3103 Net gain (loss) on financial liabilities designated at fair value, attributable to changes in credit risk Concept (Monetary) For Period Credit ifrs-full:ChangesInFairValueOfFinancialLiabilityAttributableToChangesInCreditRiskOfLiability
3104 Accumulated gain (loss) on financial liabilities designated at fair value, attributable to changes in credit risk Concept (Monetary) As Of Credit ifrs-full:AccumulatedChangesInFairValueOfFinancialLiabilityAttributableToChangesInCreditRiskOfLiability
3105 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
3106 1245 - Disclosure - Deposits by Customers - Schedule of Deposits by Customers (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDepositsByCustomersScheduleOfDepositsByCustomers
3107 Disclosure of deposits from customers [table] Table

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ck0001087711:DisclosureOfDepositsFromCustomersTable
3108 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3109 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3110 Current and Demand Accounts - [member] Member ck0001087711:CurrentAndDemandAccountsMember
3111 Savings Accounts [member] Member ck0001087711:SavingsAccountsMember
3112 Time Deposits [member] Member ck0001087711:TimeDepositsMember
3113 Amounts due to other Santander UK Group Holdings plc subsidiaries [member] Member ck0001087711:AmountsDueToOtherSantanderUKGroupHoldingsPlcSubsidiariesMember
3114 Amounts due to Santander UK Group Holdings plc [member] Member ck0001087711:AmountsDueToSantanderUkGroupHoldingsPlcMember
3115 Amounts Due to Fellow Banco Santander Subsidiaries [member] Member ck0001087711:AmountsDueToFellowBancoSantanderSubsidiariesMember
3116 Disclosure of deposits from customers [line items] LineItems ck0001087711:DisclosureOfDepositsFromCustomersLineItems
3117 Deposits from customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
3118 1246 - Disclosure - Deposits by Customers - Schedule of Deposits by Customers (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDepositsByCustomersScheduleOfDepositsByCustomersParenthetical
3119 Disclosure of deposits from customers [table] Table

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ck0001087711:DisclosureOfDepositsFromCustomersTable
3120 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3121 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3122 Equity Index Linked Deposits [member] Member ck0001087711:EquityIndexLinkedDepositsMember
3123 Disclosure of deposits from customers [line items] LineItems ck0001087711:DisclosureOfDepositsFromCustomersLineItems
3124 Deposits from customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
3125 Capital amount guaranteed or protected Concept (Monetary) As Of Credit ck0001087711:CapitalAmountGuaranteedOrProtectedInRespectOfEquityIndexLinkedDeposits
3126 Capital amount of return guaranteed Concept (Monetary) As Of Credit ck0001087711:AmountOfReturnGuaranteedInRespectOfEquityIndexLinkedDeposits
3127 1247 - Disclosure - Deposits by Banks - Schedule of Deposits by Banks (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDepositsByBanksScheduleOfDepositsByBanks
3128 Disclosure Of Deposits From Banks [table] Table

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ck0001087711:DisclosureOfDepositsFromBanksTable
3129 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3130 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3131 Items in Course of Transmission [member] Member ck0001087711:ItemsInCourseOfTransmissionMember
3132 Deposits Held as Collateral [member] Member ck0001087711:DepositsHeldAsCollateralMember
3133 Other Deposits [member] Member ck0001087711:OtherDepositsMember
3134 Amounts due to Santander UK subsidiaries [member] Member ck0001087711:AmountsDueToSantanderUKSubsidiariesMember
3135 Disclosure of deposits from banks [line items] LineItems ck0001087711:DisclosureOfDepositsFromBanksLineItems
3136 Deposits from banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
3137 1248 - Disclosure - Deposits by Banks - Schedule of Deposits by Banks (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDepositsByBanksScheduleOfDepositsByBanksParenthetical
3138 Implied Table Table

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implied:Table
3139 Disclosure of deposits from banks [abstract] Abstract ck0001087711:DisclosureOfDepositsFromBanksAbstract
3140 Drawdown from TFS Concept (Monetary) As Of Credit ck0001087711:DrawdownFromTermFundingScheme
3141 1249 - Disclosure - Repurchase Agreements - Non Trading - Summary of Repurchase Agreements Non Trading (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureRepurchaseAgreementsNonTradingSummaryOfRepurchaseAgreementsNonTrading
3142 Disclosure Of Repurchase Agreements [table] Table

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ck0001087711:DisclosureOfRepurchaseAgreementsTable
3143 Types of agreement [axis] Axis ck0001087711:TypesOfAgreementAxis
3144 Types of agreement [domain] Member ck0001087711:TypesOfAgreementDomain
3145 Agreements with banks [member] Member ck0001087711:AgreementsWithBanksMember
3146 Agreements with customers [member] Member ck0001087711:AgreementsWithCustomersMember
3147 Disclosure Of Repurchase Agreements [line items] LineItems ck0001087711:DisclosureOfRepurchaseAgreementsLineItems
3148 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
3149 1250 - Disclosure - Debt Securities In Issue - Summary of Debt Securities in Issue (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDebtSecuritiesInIssueSummaryOfDebtSecuritiesInIssue
3150 Debt Securities in Issue [Table] Table

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ck0001087711:DebtSecuritiesInIssueTable
3151 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3152 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3153 Medium Term Notes [member] Member ck0001087711:MediumTermNotes1Member
3154 Euro 35bn Global Covered Bond Programme [member] Member ck0001087711:EuroThirtyFiveBillionGlobalCoveredBondProgrammeMember
3155 Certificates of Deposit [member] Member ck0001087711:CertificateOfDepositMember
3156 Credit Linked Note [member] Member ck0001087711:CreditLinkedNoteMember
3157 Securitisation Programmes [member] Member ck0001087711:SecuritisationProgrammesMember
3158 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3159 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3160 US$30bn Euro Medium Term Note Programme [member] Member ck0001087711:USDollarThirtyBillionEuroMediumTermNoteProgrammeMember
3161 Euro 30bn Euro Medium Term Note Programme [member] Member ck0001087711:EuroThirtyBillionEuroMediumTermNoteProgrammeMember
3162 US SEC - Registered - Santander UK plc [member] Member ck0001087711:USSECRegisteredSantanderUKPlcMember
3163 US$20bn Commercial Paper Programmes [member] Member ck0001087711:USDollarTwentyBillionCommercialPaperProgrammeMember
3164 Debt securities in issue [line items] LineItems ck0001087711:DebtSecuritiesInIssueLineItems
3165 Debt Securities Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
3166 Credit Linked Notes Concept (Monetary) As Of Credit ck0001087711:CreditLinkedNotesIssued
3167 1251 - Disclosure - Debt Securities In Issue - Summary of Debt Securities in Issue (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDebtSecuritiesInIssueSummaryOfDebtSecuritiesInIssueParenthetical
3168 Debt Securities in Issue [Table] Table

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ck0001087711:DebtSecuritiesInIssueTable
3169 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3170 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3171 Medium Term Notes [member] Member ck0001087711:MediumTermNotes1Member
3172 Euro 35bn Global Covered Bond Programme [member] Member ck0001087711:EuroThirtyFiveBillionGlobalCoveredBondProgrammeMember
3173 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3174 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3175 US$30bn Euro Medium Term Note Programme [member] Member ck0001087711:USDollarThirtyBillionEuroMediumTermNoteProgrammeMember
3176 Euro 30bn Euro Medium Term Note Programme [member] Member ck0001087711:EuroThirtyBillionEuroMediumTermNoteProgrammeMember
3177 US$20bn Commercial Paper Programmes [member] Member ck0001087711:USDollarTwentyBillionCommercialPaperProgrammeMember
3178 Debt securities in issue [line items] LineItems ck0001087711:DebtSecuritiesInIssueLineItems
3179 Notional amount Concept (Monetary) As Of ifrs-full:NotionalAmount
3180 1252 - Disclosure - Debt Securities In Issue - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureDebtSecuritiesInIssueAdditionalInformation
3181 Debt Securities in Issue [Table] Table

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ck0001087711:DebtSecuritiesInIssueTable
3182 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3183 Equity [member] Member ifrs-full:EquityMember
3184 PSA Finance UK Limited [member] Member ck0001087711:PSAFinanceUKLimitedMember
3185 Debt securities in issue [line items] LineItems ck0001087711:DebtSecuritiesInIssueLineItems
3186 Percentage of losses in portfolio having credit protection Concept (Percent) For Period ck0001087711:PercentageOfLossesInPortfolioHavingCreditProtection
3187 1253 - Disclosure - Subordinated Liabilities - Schedule of Subordinated Liabilities (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSubordinatedLiabilitiesScheduleOfSubordinatedLiabilities
3188 Implied Table Table

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implied:Table
3189 Disclosure of Subordinated Liabilities [abstract] Abstract ck0001087711:DisclosureOfSubordinatedLiabilitiesAbstract
3190 £325m Sterling Preference Shares Concept (Monetary) As Of Credit ck0001087711:SterlingPreferenceShares
3191 £175m Fixed/Floating Rate Tier One Preferred Income Capital Securities Concept (Monetary) As Of Credit ck0001087711:FixedFloatingRateTierOnePreferredIncomeCapitalSecurities
3192 Undated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:UndatedSubordinatedLiabilities
3193 Dated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:DatedSubordinatedLiabilities
3194 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
3195 1254 - Disclosure - Subordinated Liabilities - Schedule of Subordinated Liabilities (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSubordinatedLiabilitiesScheduleOfSubordinatedLiabilitiesParenthetical
3196 Implied Table Table

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implied:Table
3197 Disclosure of Subordinated Liabilities [abstract] Abstract ck0001087711:DisclosureOfSubordinatedLiabilitiesAbstract
3198 325m Sterling Preference Shares, Notional amount Concept (Monetary) As Of ck0001087711:SterlingPreferenceSharesNotionalAmount
3199 175m Fixed/Floating Rate Tier One Preferred Income Capital Securities, Notional amount Concept (Monetary) As Of ck0001087711:FixedFloatingRateTierOnePreferredIncomeCapitalSecuritiesNotionalAmount
3200 1255 - Disclosure - Subordinated Liabilities - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSubordinatedLiabilitiesAdditionalInformation
3201 Disclosure of Subordinated Liabilities [table] Table

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ck0001087711:DisclosureOfSubordinatedLiabilitiesTable
3202 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3203 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3204 300m Fixed/Floating Rate Non-Cumulative Callable Preference Shares [member] Member ck0001087711:ThreeHundredMillionFixedOrFloatingRateNoncumulativeCallablePreferenceSharesMember
3205 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001087711:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3206 Classes of Share Capital [Axis] Axis ifrs-full:ClassesOfShareCapitalAxis
3207 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
3208 175m Sterling Fixed/Floating Rate Tier One Preferred Income Capital Securities [member] Member ck0001087711:OneSeventyFiveMillionPoundSterlingFixedFloatingRateTierOnePreferredIncomeCapitalSecuritiesMember
3209 10.0625% non-cumulative non-redeemable sterling preference shares [member] Member ck0001087711:TenPointZeroSixTwoFivePercentNoncumulativeNonredeemableSterlingPreferenceSharesMember
3210 10.375% non-cumulative non-redeemable sterling preference shares [member] Member ck0001087711:TenPointThreeSevenFivePercentNoncumulativeNonredeemableSterlingPreferenceSharesMember
3211 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3212 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3213 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
3214 7.125% 30 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointOneTwoFivePercentThirtyYearStepupPerpetualCallableSubordinatedNotesMember
3215 10.0625% Exchangeable Capital Securities [member] Member ck0001087711:TenPointZeroSixTwoFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3216 10.375% exchangeable subordinated capital securities [member] Member ck0001087711:TenPointThreeSevenFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3217 10.125% Subordinated Guaranteed Bond 2023 [member] Member ck0001087711:TenPointOneTwoFivePercentSubordinatedGuaranteedBondTwentyTwentyThreeMember
3218 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3219 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3220 Santander UK Plc [member] Member ck0001087711:SantanderUkPlcMember
3221 Disclosure of subordinated liabilities [line items] LineItems ck0001087711:DisclosureOfSubordinatedLiabilitiesLineItems
3222 Notional amount Concept (Monetary) As Of ck0001087711:FixedFloatingRateTierOnePreferredIncomeCapitalSecuritiesNotionalAmount
3223 Notional amount Concept (Monetary) As Of ck0001087711:StepUpCallablePerpetualReserveCapitalInstrumentsNotionalAmount
3224 Defaults of principal, interest or other breaches with respect to subordinated liabilities Concept (Monetary) As Of Credit ck0001087711:DefaultsOfPrincipalInterestOrOtherBreachesWithRespectToSubordinatedLiabilities
3225 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
3226 Par value per share Concept (Share) As Of ifrs-full:ParValuePerShare
3227 1256 - Disclosure - Subordinated Liabilities - Summary of Undated Subordinated Liabilities (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfUndatedSubordinatedLiabilities
3228 Disclosure of Subordinated Liabilities [table] Table

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ck0001087711:DisclosureOfSubordinatedLiabilitiesTable
3229 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3230 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3231 10.0625% Exchangeable Capital Securities [member] Member ck0001087711:TenPointZeroSixTwoFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3232 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
3233 7.125% 30 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointOneTwoFivePercentThirtyYearStepupPerpetualCallableSubordinatedNotesMember
3234 Disclosure of subordinated liabilities [line items] LineItems ck0001087711:DisclosureOfSubordinatedLiabilitiesLineItems
3235 Undated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:UndatedSubordinatedLiabilities
3236 First call date Concept (Text/String) For Period ck0001087711:InitialCallDateOfUndatedSubordinatedLiabilities
3237 1257 - Disclosure - Subordinated Liabilities - Summary of Undated Subordinated Liabilities (Parenthetical) (Detail) Network

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3238 Disclosure of Subordinated Liabilities [table] Table

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ck0001087711:DisclosureOfSubordinatedLiabilitiesTable
3239 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3240 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3241 10.0625% Exchangeable Capital Securities [member] Member ck0001087711:TenPointZeroSixTwoFivePercentExchangeableSubordinatedCapitalSecuritiesMember
3242 7.375% 20 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointThreeSevenFivePercentTwentyYearStepupPerpetualCallableSubordinatedNotesMember
3243 7.125% 30 Year Step-up Perpetual Callable Subordinated Notes [member] Member ck0001087711:SevenPointOneTwoFivePercentThirtyYearStepupPerpetualCallableSubordinatedNotesMember
3244 Disclosure of subordinated liabilities [line items] LineItems ck0001087711:DisclosureOfSubordinatedLiabilitiesLineItems
3245 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
3246 Notes maturity, year Concept (xbrli:durationItemType) For Period ck0001087711:BorrowingsMaturityPeriod
3247 Maturity period Concept (Text/String) For Period ifrs-full:BorrowingsMaturity
3248 1258 - Disclosure - Subordinated Liabilities - Summary of Dated Subordinated Liabilities (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureSubordinatedLiabilitiesSummaryOfDatedSubordinatedLiabilities
3249 Disclosure of Subordinated Liabilities [table] Table

*

*

ck0001087711:DisclosureOfSubordinatedLiabilitiesTable
3250 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3251 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3252 10.125% Subordinated Guaranteed Bond 2023 [member] Member ck0001087711:TenPointOneTwoFivePercentSubordinatedGuaranteedBondTwentyTwentyThreeMember
3253 9.625% Subordinated Notes 2023 [member] Member ck0001087711:NinePointSixTwoFivePercentSubordinatedNotesTwentyTwentyThreeMember
3254 5% Subordinated Notes 2023 [member] Member ck0001087711:FivePercentSubordinatedNotesTwentyTwentyThreeMember
3255 4.75% Subordinated Notes 2025 [member] Member ck0001087711:FourPointSevenFivePercentSubordinatedNotesTwentyTwentyFiveMember
3256 7.95% Subordinated Notes 2029 [member] Member ck0001087711:SevenPointNineFivePercentSubordinatedNotesTwentyTwentyNineMember
3257 6.50% Subordinated Notes 2030 [member] Member ck0001087711:SixPointFivePercentSubordinatedNotesTwentyThirtyMember
3258 8.963% Subordinated Notes 2045 [member] Member ck0001087711:EightPointNineSixThreePercentNotesTwentyFortyFiveMember
3259 5.875% Subordinated Notes 2031 [member] Member ck0001087711:FivePointEightSevenFivePercentSubordinatedNotesTwentyThirtyOneMember
3260 5.625% Subordinated Notes 2045 [member] Member ck0001087711:FivePointSixTwoFivePercentSubordinatedNotesTwentyFortyFiveMember
3261 Disclosure of subordinated liabilities [line items] LineItems ck0001087711:DisclosureOfSubordinatedLiabilitiesLineItems
3262 Dated subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:DatedSubordinatedLiabilities
3263 Maturity period Concept (Text/String) For Period ifrs-full:BorrowingsMaturity
3264 1259 - Disclosure - Subordinated Liabilities - Summary of Dated Subordinated Liabilities (Parenthetical) (Detail) Network

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3265 Disclosure of Subordinated Liabilities [table] Table

*

*

ck0001087711:DisclosureOfSubordinatedLiabilitiesTable
3266 Types of Financial Liabilities [Axis] Axis ifrs-full:TypesOfFinancialLiabilitiesAxis
3267 Financial liabilities, type [member] Member ifrs-full:FinancialLiabilitiesTypeMember
3268 10.125% Subordinated Guaranteed Bond 2023 [member] Member ck0001087711:TenPointOneTwoFivePercentSubordinatedGuaranteedBondTwentyTwentyThreeMember
3269 9.625% Subordinated Notes 2023 [member] Member ck0001087711:NinePointSixTwoFivePercentSubordinatedNotesTwentyTwentyThreeMember
3270 5% Subordinated Notes 2023 [member] Member ck0001087711:FivePercentSubordinatedNotesTwentyTwentyThreeMember
3271 4.75% Subordinated Notes 2025 [member] Member ck0001087711:FourPointSevenFivePercentSubordinatedNotesTwentyTwentyFiveMember
3272 7.95% Subordinated Notes 2029 [member] Member ck0001087711:SevenPointNineFivePercentSubordinatedNotesTwentyTwentyNineMember
3273 6.50% Subordinated Notes 2030 [member] Member ck0001087711:SixPointFivePercentSubordinatedNotesTwentyThirtyMember
3274 8.963% Subordinated Notes 2045 [member] Member ck0001087711:EightPointNineSixThreePercentNotesTwentyFortyFiveMember
3275 5.875% Subordinated Notes 2031 [member] Member ck0001087711:FivePointEightSevenFivePercentSubordinatedNotesTwentyThirtyOneMember
3276 5.625% Subordinated Notes 2045 [member] Member ck0001087711:FivePointSixTwoFivePercentSubordinatedNotesTwentyFortyFiveMember
3277 Disclosure of subordinated liabilities [line items] LineItems ck0001087711:DisclosureOfSubordinatedLiabilitiesLineItems
3278 Interest rate Concept (Percent) As Of ifrs-full:BorrowingsInterestRate
3279 Notional amount Concept (Monetary) As Of Credit ck0001087711:SubordinatedNotesNotionalAmount
3280 1260 - Disclosure - Provisions - Summary of Provisions Reconciliation (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureProvisionsSummaryOfProvisionsReconciliation
3281 Disclosure of other provisions [table] Table

*

*

ifrs-full:DisclosureOfOtherProvisionsTable
3282 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3283 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3284 FSCS and Bank Levy [member] Member ck0001087711:FSCSAndBankLevyMember
3285 PPI [member] Member ck0001087711:PPIMember
3286 Other products [member] Member ck0001087711:OtherProductsMember
3287 Vacant Property [member] Member ck0001087711:VacantPropertyMember
3288 Off-Balance Sheet [member] Member ck0001087711:OffBalanceSheetMember
3289 Regulatory and other [member] Member ck0001087711:RegulatoryAndOtherMember
3290 Maturity [axis] Axis ifrs-full:MaturityAxis
3291 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3292 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3293 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
3294 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3295 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Provisions
3296 Reallocation of ECL on off-balance sheet exposures Concept (Monetary) For Period Credit ck0001087711:ReallocationOfExpectedCreditLossOnUndrawnExposuresRelatedToLoanCommitments
3297 Balance on January 1 2018 Concept (Monetary) As Of Credit ck0001087711:ProvisionsOnAdoptionOfIFRS9
3298 Additional provisions Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
3299 Provisions released (see Note 8) Concept (Monetary) For Period Debit ifrs-full:UnusedProvisionReversedOtherProvisions
3300 Utilisation Concept (Monetary) For Period Debit ifrs-full:ProvisionUsedOtherProvisions
3301 Other Concept (Monetary) For Period Credit ifrs-full:NewProvisionsOtherProvisions
3302 Transfers Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesOtherProvisions
3303 Ending balance Concept (Monetary) As Of Credit ifrs-full:Provisions
3304 To be settled: Abstract ck0001087711:ToBeSettledAbstract
3305 Ending balance Concept (Monetary) As Of Credit ifrs-full:Provisions
3306 1261 - Disclosure - Provisions - Summary of Provisions Reconciliation (Parenthetical) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureProvisionsSummaryOfProvisionsReconciliationParenthetical
3307 Disclosure of other provisions [table] Table

*

*

ifrs-full:DisclosureOfOtherProvisionsTable
3308 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3309 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3310 FSCS and Bank Levy [member] Member ck0001087711:FSCSAndBankLevyMember
3311 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3312 Other Concept (Monetary) For Period Credit ifrs-full:NewProvisionsOtherProvisions
3313 1262 - Disclosure - Provisions - Additional Information (Detail) Network

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*

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3314 Disclosure of other provisions [table] Table

*

*

ifrs-full:DisclosureOfOtherProvisionsTable
3315 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3316 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3317 PPI [member] Member ck0001087711:PPIMember
3318 Provision for Past Business Review [member] Member ck0001087711:ProvisionForPastBusinessReviewMember
3319 August 2016 FCA Papers [member] Member ck0001087711:AugustTwoThousandSixteenFCAPapersMember
3320 Other products [member] Member ck0001087711:OtherProductsMember
3321 FSCS And Bank Levy Financial Services Compensation Scheme [member] Member ck0001087711:FscsAndBankLevyFinancialServicesCompensationSchemeMember
3322 Regulatory Related Uk Bank Levy [member] Member ck0001087711:RegulatoryRelatedUKBankLevyMember
3323 Compliance with Consumer Credit Act [member] Member ck0001087711:ComplianceWithConsumerCreditActMember
3324 Historical probate and bereavement practices [member] Member ck0001087711:HistoricalProbateAndBereavementPracticesMember
3325 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3326 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3327 Financial Ombudsman Service [member] Member ck0001087711:FinancialOmbudsmanServiceMember
3328 Santander UK Group Holdings plc [member] Member ifrs-full:ParentMember
3329 Key Drivers PPI [axis] Axis ck0001087711:KeyDriversPPIAxis
3330 Key Drivers PPI [domain] Member ck0001087711:KeyDriversPpiDomain
3331 Plevin redress [member] Member ck0001087711:PlevinRedressMember
3332 Range [axis] Axis ifrs-full:RangeAxis
3333 Ranges [member] Member ifrs-full:RangesMember
3334 Top of Range [member] Member ifrs-full:TopOfRangeMember
3335 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3336 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3337 Provision linked to future claims levels Concept (Monetary) For Period Credit ck0001087711:FutureExpectedProvisionAmount
3338 Impact on the PPI misselling element of provision Concept (Monetary) For Period Debit ck0001087711:SensitivityAnalysisIncreaseDecreaseInProvisionValue
3339 Overturn rate percentage Concept (Percent) For Period ck0001087711:OverturnRatePercentage
3340 Average overturn rate percentage Concept (Percent) For Period ck0001087711:AverageOverturnRatePercentage
3341 Provisions Concept (Monetary) As Of Credit ifrs-full:Provisions
3342 Additional provision charge Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
3343 Provisions released Concept (Monetary) For Period Debit ifrs-full:UnusedProvisionReversedOtherProvisions
3344 Reduction in amount that FSCS owes to HM Treasury Concept (Monetary) As Of Credit ck0001087711:AmountPayableToHmTreasury
3345 Regulatory costs related to Financial Services Compensation Scheme (FSCS) Concept (Monetary) For Period Debit ck0001087711:ExpensesRelatedToFinancialServicesCompensationScheme
3346 Bank levy rate Concept (Percent) For Period ck0001087711:BankLevyRate
3347 UK Bank Levy Concept (Percent) For Period ck0001087711:UKBankLevyRate
3348 Cost of UK Bank Levy Incurred Concept (Monetary) For Period Debit ck0001087711:ExpensesRelatedToUKBankLevy
3349 Amount paid as UK Bank Levy Concept (Monetary) For Period Debit ck0001087711:UKBankLevyPaid
3350 Additional operational risk losses and restructuring charges Concept (Monetary) For Period Credit ck0001087711:AdditionalProvisionsOtherProvisionsOperationalRiskLossesAndRestructuringCharges
3351 1263 - Disclosure - Provisions - Summary of Key Drivers of PPI Provision Balance and Forecast Assumptions Used in Calculating Provision (Detail) Network

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3352 Disclosure of other provisions [table] Table

*

*

ifrs-full:DisclosureOfOtherProvisionsTable
3353 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3354 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3355 PPI [member] Member ck0001087711:PPIMember
3356 Key Drivers PPI [axis] Axis ck0001087711:KeyDriversPPIAxis
3357 Key Drivers PPI [domain] Member ck0001087711:KeyDriversPpiDomain
3358 Inbound Complaints [member] Member ck0001087711:InboundComplaintsMember
3359 Outbound Complaints [member] Member ck0001087711:OutboundComplaintsMember
3360 Response Rate to Outbound Contact [member] Member ck0001087711:ResponseRateToOutboundContactMember
3361 Average Uphold Rate Per Claim [member] Member ck0001087711:AverageUpholdRatePerClaimMember
3362 Average Redress Per Claim [member] Member ck0001087711:AverageRedressPerClaimMember
3363 Disclosure of other provisions [line items] LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
3364 Cumulative to 31 December 2018 Concept (Percent) For Period ck0001087711:ProvisionCumulativeToYearEndRate
3365 Cumulative to 31 December 2018 Concept (Integer) For Period ck0001087711:ProvisionCumulativeToYearEndNumber
3366 Cumulative to 31 December 2018 Concept (Monetary) For Period Credit ck0001087711:ProvisionCumulativeToYearEndAmount
3367 Future expected (unaudited) Concept (Percent) For Period ck0001087711:FutureExpectedProvisionRate
3368 Future expected (unaudited) Concept (Integer) For Period ck0001087711:FutureExpectedProvisionNumber
3369 Future expected (unaudited) Concept (Monetary) For Period Credit ck0001087711:FutureExpectedProvisionAmount
3370 Sensitivity analysis rate Concept (Percent) For Period ck0001087711:SensitivityAnalysisRate
3371 Sensitivity analysis number Concept (Integer) For Period ck0001087711:SensitivityAnalysisNumber
3372 Sensitivity analysis amount Concept (Monetary) For Period Debit ck0001087711:SensitivityAnalysisAmount
3373 Sensitivity analysis increase/decrease in provision Concept (Monetary) For Period Debit ck0001087711:SensitivityAnalysisIncreaseDecreaseInProvisionValue
3374 1264 - Disclosure - Provisions - Summary of Key Drivers of PPI Provision Balance and Forecast Assumptions Used in Calculating Provision (Parenthetical) (Detail) Network

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3375 Implied Table Table

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*

implied:Table
3376 Disclosure of other provisions [abstract] Abstract ifrs-full:DisclosureOfOtherProvisionsAbstract
3377 Cumulative average value Concept (Monetary) For Period Credit ck0001087711:CumulativeAverageValue
3378 Future average value Concept (Monetary) For Period Credit ck0001087711:FutureAverageValue
3379 1265 - Disclosure - Retirement Benefit Plans - Summary of Retirement Benefit Plans (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureRetirementBenefitPlansSummaryOfRetirementBenefitPlans
3380 Disclosure of net defined benefit liability (asset) [table] Table

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*

ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3381 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
3382 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
3383 Surplus [member] Member ck0001087711:SurplusMember
3384 Deficit [member] Member ck0001087711:DeficitsMember
3385 Legal entity [axis] Axis dei:LegalEntityAxis
3386 Entity [Domain] Member dei:EntityDomain
3387 Santander UK Group [member] Member ck0001087711:SantanderUKGroupMember
3388 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3389 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3390 Funded Defined Benefit Pension Scheme [member] Member ifrs-full:WhollyOrPartlyFundedDefinedBenefitPlansMember
3391 Unfunded Defined Benefit Pension Scheme [member] Member ifrs-full:WhollyUnfundedDefinedBenefitPlansMember
3392 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3393 Assets/(liabilities) Abstract ifrs-full:NetAssetsLiabilitiesAbstract
3394 Surplus (deficit) in plan Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
3395 Total net assets Concept (Monetary) As Of Debit ifrs-full:PlanAssetsAtFairValue
3396 1266 - Disclosure - Retirement Benefit Plans - Summary of Remeasurement (Gains)/Losses Recognised In Other Comprehensive Income (Detail) Network

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3397 Implied Table Table

*

*

implied:Table
3398 Disclosure of net defined benefit liability (asset) [abstract] Abstract ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetAbstract
3399 Pension remeasurement Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
3400 1267 - Disclosure - Retirement Benefit Plans - Additional Information (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureRetirementBenefitPlansAdditionalInformation
3401 Disclosure of defined benefit plans [table] Table

*

*

ifrs-full:DisclosureOfDefinedBenefitPlansTable
3402 Service concession arrangements [axis] Axis ifrs-full:ServiceConcessionArrangementsAxis
3403 Service concession arrangements [member] Member ifrs-full:ServiceConcessionArrangementsMember
3404 Deficit Repair Contributions [member] Member ck0001087711:DeficitRepairContributionsPlanMember
3405 Deficit Repair Group Section Contributions [member] Member ck0001087711:DeficitRepairGroupSectionContributionsPlanMember
3406 Deficit Group Section Contributions Plan [member] Member ck0001087711:DeficitGroupSectionContributionsPlanMember
3407 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3408 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3409 Santander UK Plc [member] Member ck0001087711:SantanderUkPlcMember
3410 Santander UK Group [member] Member ck0001087711:SantanderUKGroupMember
3411 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3412 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3413 Present value of defined benefit obligations [member] Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
3414 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3415 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3416 Equity collar [member] Member ck0001087711:EquityCollarMember
3417 Legal entity [axis] Axis dei:LegalEntityAxis
3418 Entity [Domain] Member dei:EntityDomain
3419 Santander CF Trustee Limited [member] Member ck0001087711:SantanderCFTrusteeLimitedMember
3420 Santander (UK) Group Pension Scheme Trustees Limited [member] Member ck0001087711:SantanderUkGroupPensionSchemeTrusteesLimitedMember
3421 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
3422 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
3423 Actuarial Assumption of Discount Rates [member] Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
3424 Actuarial Assumption of Expected Rates of Inflation [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfInflationMember
3425 Actuarial assumption of expected rate of pension increases [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfPensionIncreasesMember
3426 Actuarial assumption of mortality rates [member] Member ifrs-full:ActuarialAssumptionOfMortalityRatesMember
3427 Disclosure of defined benefit plans [line items] LineItems ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
3428 Defined contribution expense Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
3429 Key management personnel expense Concept (Text/String) For Period ifrs-full:ExplanationOfValueAssignedToKeyAssumption
3430 Percentage of employee covered defined benefit pension schemes Concept (Percent) As Of ifrs-full:LevelOfParticipationOfEntityComparedWithOtherParticipatingEntities
3431 Number of directors selected Concept (Integer) For Period ck0001087711:NumberOfBoardOfDirectorsInSubsidiary
3432 Number of directors nominated Concept (Integer) For Period ck0001087711:NumberOfNominatedDirectorsInSubsidiary
3433 Number of trustee directors Concept (Integer) For Period ck0001087711:NumberOfTrusteeDirectorsAppointed
3434 Actuarial valuation deficit Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleDecreaseInActuarialAssumption
3435 Estimated increase in liabilities in relation to judgment on GMP equalisation Concept (Monetary) For Period Debit ifrs-full:GainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
3436 Gross notional value Concept (Monetary) As Of Credit ck0001087711:GrossNotionalValuePensionScheme
3437 Equity securities hold Concept (Monetary) As Of Debit ifrs-full:DescriptionOfAmountsOfEntitysOwnFinancialInstrumentsIncludedInFairValueOfPlanAssets
3438 Property occupied Concept (Monetary) As Of Debit ifrs-full:DescriptionOfAmountsOfPropertyOccupiedByEntityIncludedInFairValueOfPlanAssets
3439 Other assets occupied Concept (Monetary) As Of Debit ifrs-full:DescriptionOfAmountsOfOtherAssetsUsedByEntityIncludedInFairValueOfPlanAssets
3440 Contribution to scheme based on agreement Concept (Monetary) As Of Credit ck0001087711:FundingToNewRecoveryPlanBasedOnNewAgreement
3441 Contributions to defined benefit plans Concept (Monetary) For Period Debit ck0001087711:ContributionsToDefinedBenefitPlans
3442 Annual increase in contibution Concept (Percent) For Period ck0001087711:PercentageOfAnnualIncreaseInContributionsToPensionScheme
3443 Maturity date for contribution Concept (Text/String) For Period ifrs-full:DescriptionOfFundingArrangementsAndFundingPolicyThatAffectFutureContributions
3444 Surplus (deficit) in plan Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
3445 Improvements to life expectancy of female employees Concept (Percent) For Period ck0001087711:LifeExpectancyImprovementRateOfFemaleEmployees
3446 Improvements to life expectancy of male employees Concept (Percent) For Period ck0001087711:LifeExpectancyImprovementRateOfMaleEmployees
3447 Average duration of defined benefit obligation Concept (Text/String) For Period ck0001087711:DefinedBenefitObligationWeightedAverageDuration
3448 1268 - Disclosure - Retirement Benefit Plans - Total Defined Benefit Plan Amount Charged to Income Statement (Detail) Network

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3449 Implied Table Table

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*

implied:Table
3450 Disclosure of net defined benefit liability (asset) [abstract] Abstract ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetAbstract
3451 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
3452 Current service cost Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
3453 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
3454 Administration costs Concept (Monetary) For Period Credit ck0001087711:AdministrationCostsNetDefinedBenefitLiabilityAsset
3455 Total Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInNetDefinedBenefitLiabilityAsset
3456 1269 - Disclosure - Retirement Benefit Plans - Summary of Amounts Recognised in Other Comprehensive Income (Detail) Network

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3457 Implied Table Table

*

*

implied:Table
3458 Disclosure of net defined benefit liability (asset) [abstract] Abstract ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetAbstract
3459 Return on plan assets (excluding amounts included in net interest expense) Concept (Monetary) For Period Debit ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
3460 Actuarial (gains)/losses arising from changes in demographic assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
3461 Actuarial gains arising from experience adjustments Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
3462 Actuarial (gains)/losses arising from changes in financial assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
3463 Pension remeasurement Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
3464 1270 - Disclosure - Retirement Benefit Plans - Disclosure of Movements in Present Value of Defined Benefit Obligations (Detail) Network

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3465 Disclosure of net defined benefit liability (asset) [table] Table

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ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3466 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3467 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3468 Present value of defined benefit obligations [member] Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
3469 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
3470 Beginning balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3471 Current service cost Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
3472 Current service cost paid by subsidiaries Concept (Monetary) For Period Credit ck0001087711:CurrentServiceCostPaidBySubsidiaries
3473 Current service cost paid by fellow Banco Santander subsidiaries Concept (Monetary) For Period Credit ck0001087711:CurrentServiceCostPaidByFellowBancoSantanderSubsidiaries
3474 Net interest income Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
3475 Employer salary sacrifice contributions Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
3476 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
3477 GMP equalisation cost Concept (Monetary) For Period Debit ifrs-full:GainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
3478 Remeasurement due to actuarial movements arising from: Abstract ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAssetAbstract
3479 - Changes in demographic assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
3480 - Experience adjustments Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
3481 - Changes in financial assumptions Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
3482 Benefits paid Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
3483 Ending balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3484 1271 - Disclosure - Retirement Benefit Plans - Disclosure of Movements in Fair Value of Scheme Assets (Detail) Network

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3485 Disclosure of net defined benefit liability (asset) [table] Table

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*

ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
3486 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
3487 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
3488 Fair value of scheme assets [member] Member ifrs-full:PlanAssetsMember
3489 Disclosure of net defined benefit liability (asset) [line items] LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
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3497 Ending balance Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
3498 1272 - Disclosure - Retirement Benefit Plans - Summary of Composition and Fair Value of Plan Assets (Detail) Network

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3499 Disclosure of net defined benefit liability (asset) [table] Table

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3502 Quoted Prices in Active Markets [member] Member ck0001087711:QuotedPricesInActiveMarketsMember
3503 Prices Not Quoted in Active Markets [member] Member ck0001087711:PricesNotQuotedInActiveMarketsMember
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3506 Overseas equities Concept (Percent) As Of ck0001087711:OverseasEquitiesPercentageContributedToFairValueOfPlanAssets
3507 Corporate bonds Concept (Percent) As Of ck0001087711:CorporateBondsPercentageContributedToFairValueOfPlanAssets
3508 Government fixed interest bonds Concept (Percent) As Of ck0001087711:GovernmentFixedInterestBondsPercentageContributedToFairValueOfPlanAssets
3509 Government index-linked bonds Concept (Percent) As Of ck0001087711:GovernmentIndexlinkedBondsPercentageContributedToFairValueOfPlanAssets
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3511 Derivatives Concept (Percent) As Of ck0001087711:DerivativesPercentageContributedToFairValueOfPlanAssets
3512 Cash Concept (Percent) As Of ck0001087711:CashAndCashEquivalentsPercentageContributedToFairValueOfPlanAssets
3513 Repurchase agreements Concept (Percent) As Of ck0001087711:RepurchaseAgreementsPercentageContributedToFairValueOfPlanAssets
3514 Other Concept (Percent) As Of ck0001087711:OtherAssetsPercentageContributedToFairValueOfPlanAssets
3515 Total Concept (Percent) As Of ck0001087711:PercentagesContributedToFairValueOfPlanAssets
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3517 Overseas equities Concept (Monetary) As Of Debit ck0001087711:OverseasEquitiesAmountContributedToFairValueOfPlanAssets
3518 Corporate bonds Concept (Monetary) As Of Debit ck0001087711:CorporateBondsAmountContributedToFairValueOfPlanAssets
3519 Government fixed interest bonds Concept (Monetary) As Of Debit ck0001087711:GovernmentFixedInterestBondsAmountContributedToFairValueOfPlanAssets
3520 Government index-linked bonds Concept (Monetary) As Of Debit ck0001087711:GovernmentIndexlinkedBondsAmountContributedToFairValueOfPlanAssets
3521 Property Concept (Monetary) As Of Debit ifrs-full:PropertyAmountContributedToFairValueOfPlanAssets
3522 Derivatives Concept (Monetary) As Of Debit ifrs-full:DerivativesAmountContributedToFairValueOfPlanAssets
3523 Cash Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalentsAmountContributedToFairValueOfPlanAssets
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3525 Other Concept (Monetary) As Of Debit ifrs-full:OtherAssetsAmountContributedToFairValueOfPlanAssets
3526 Total Concept (Monetary) As Of Debit ck0001087711:AggregateAmountContributedToFairValueOfPlanAssets
3527 1273 - Disclosure - Retirement Benefit Plans - Summary of Principal Actuarial Assumptions Used for Defined Benefit Schemes (Detail) Network

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3528 Implied Table Table

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implied:Table
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3531 - General price inflation Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfInflation
3532 - General salary increase Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreases
3533 - Expected rate of pension increase Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfPensionIncreases
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3536 - Females Concept (xbrli:durationItemType) For Period ck0001087711:LongevityForCurrentPensionersFemalesOne
3537 Longevity at 60 for future pensioners currently aged 40, on the valuation date: Abstract ck0001087711:LongevityAtSixtyForFuturePensionersCurrentlyAgedFortyOnValuationDateAbstract
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3539 - Females Concept (xbrli:durationItemType) For Period ck0001087711:LongevityForFuturePensionersFemalesOne
3540 1274 - Disclosure - Retirement Benefit Plans - Summary of Actuarial Assumption Sensitivities (Detail) Network

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3541 Disclosure of sensitivity analysis for actuarial assumptions [table] Table

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*

ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsTable
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3544 Actuarial Assumption of Discount Rates [member] Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
3545 Actuarial Assumption of Expected Rates of Inflation [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfInflationMember
3546 Actuarial assumption of expected rates of salary increases [member] Member ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreasesMember
3547 Actuarial Assumption of Expected Rates of Mortality [member] Member ck0001087711:ActuarialAssumptionOfExpectedRatesOfMortalityMember
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3549 Increase decrease in defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleIncreaseInActuarialAssumption
3550 Description of changes in methods and assumptions Concept (Text/String) For Period ifrs-full:DescriptionOfChangesInMethodsAndAssumptionsUsedInPreparingSensitivityAnalysisForActuarialAssumptions
3551 1275 - Disclosure - Retirement Benefit Plans - Disclosure of Benefits Expected To Be Paid (Detail) Network

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3552 Disclosure of net defined benefit liability (asset) [table] Table

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*

ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
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3555 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3556 Later Than 1 Year and Not Later Than 2 Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
3557 2 - 3 years [member] Member ifrs-full:LaterThanTwoYearsAndNotLaterThanThreeYearsMember
3558 3 - 4 years [member] Member ifrs-full:LaterThanThreeYearsAndNotLaterThanFourYearsMember
3559 4 - 5 years [member] Member ifrs-full:LaterThanFourYearsAndNotLaterThanFiveYearsMember
3560 Five Years Ending 2028 [member] Member ifrs-full:LaterThanFiveYearsAndNotLaterThanTenYearsMember
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3562 Benefits expected to be paid Concept (Monetary) As Of Credit ck0001087711:DefinedBenefitPlanExpectedFutureBenefitPayments
3563 1276 - Disclosure - Contingent Liabilities and Commitments - Summary of Contingent Liabilities and Commitments (Detail) Network

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3564 Disclosure of contingent liabilities [table] Table

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ifrs-full:DisclosureOfContingentLiabilitiesTable
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3567 Contingent Liability for Guarantees [Member] Member ifrs-full:ContingentLiabilityForGuaranteesMember
3568 Loan commitments [member] Member ifrs-full:LoanCommitmentsMember
3569 Maturity [axis] Axis ifrs-full:MaturityAxis
3570 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3571 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3572 More than One Year [member] Member ifrs-full:LaterThanOneYearMember
3573 Disclosure of contingent liabilities and commitments [line items] LineItems ck0001087711:DisclosureOfContingentLiabilitiesAndCommitmentsLineItems
3574 Guarantees given to third parties Concept (Monetary) As Of Credit ck0001087711:GuaranteesGivenToThirdParties
3575 Formal standby facilities, credit lines and other commitments Concept (Monetary) As Of Credit ck0001087711:StandbyFacilitiesCreditLinesAndOtherCommitments
3576 Guarantees and formal standby facilities, credit lines and other commitments Concept (Monetary) As Of Credit ck0001087711:EstimatedFinancialEffectOfContingentLiabilitiesAndCommitments
3577 1277 - Disclosure - Contingent Liabilities and Commitments - Additional Information (Detail) Network

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3578 Disclosure of contingent liabilities [table] Table

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*

ifrs-full:DisclosureOfContingentLiabilitiesTable
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3580 Entity [Domain] Member dei:EntityDomain
3581 Visa Europe Ltd [member] Member ck0001087711:VisaEuropeLtdMember
3582 Range [axis] Axis ifrs-full:RangeAxis
3583 Ranges [member] Member ifrs-full:RangesMember
3584 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3585 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
3586 Other provisions [member] Member ifrs-full:OtherProvisionsMember
3587 Compliance with Consumer Credit Act [member] Member ck0001087711:ComplianceWithConsumerCreditActMember
3588 Disclosure of contingent liabilities and commitments [line items] LineItems ck0001087711:DisclosureOfContingentLiabilitiesAndCommitmentsLineItems
3589 Additional operational risk losses and restructuring charges Concept (Monetary) For Period Credit ck0001087711:AdditionalProvisionsOtherProvisionsOperationalRiskLossesAndRestructuringCharges
3590 Sale of share capital Concept (Percent) For Period ck0001087711:VisaEuropeLtdSaleToVisaInc
3591 Losses on litigation settlements Concept (Monetary) For Period Debit ifrs-full:LossesOnLitigationSettlements
3592 Amount of preferred stock upon indemnity more than one billion Concept (Monetary) For Period Debit ck0001087711:AmountOfPreferredStockUponIndemnityMoreThanOneBillion
3593 Description of material leasing arrangements by lessee classified as operating lease Concept (Text/String) For Period ifrs-full:DescriptionOfMaterialLeasingArrangementsByLesseeClassifiedAsOperatingLease
3594 Minimum lease extension period Concept (xbrli:durationItemType) For Period ck0001087711:MinimumLeaseExtensionPeriod
3595 Terms of notice period Concept (xbrli:durationItemType) For Period ck0001087711:TermsOfNoticePeriod
3596 Rental expense Concept (Monetary) For Period Debit ifrs-full:RentalExpense
3597 Minimum rentals Concept (Monetary) For Period Debit ifrs-full:MinimumOperatingLeasePayments
3598 Sub-lease rental income Concept (Monetary) For Period Debit ifrs-full:SubleasePaymentsRecognisedAsExpense
3599 Contingent rent expense Concept (Monetary) For Period Debit ifrs-full:ContingentRentsRecognisedAsExpenseClassifiedAsOperatingLease
3600 1278 - Disclosure - Contingent Liabilities and Commitments - Operating Lease Commitments (Detail) Network

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3601 Disclosure of finance lease and operating lease by lessee [table] Table

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ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeTable
3602 Maturity [axis] Axis ifrs-full:MaturityAxis
3603 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
3604 Not Later Than 1 Year [member] Member ifrs-full:NotLaterThanOneYearMember
3605 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
3606 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
3607 Disclosure of finance lease and operating lease by lessee [line items] LineItems ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeLineItems
3608 Lease payments Concept (Monetary) As Of Credit ifrs-full:MinimumLeasePaymentsPayableUnderNoncancellableOperatingLease
3609 1279 - Disclosure - Share Capital - Schedule of Share Capital Issued and Fully Paid (Detail) Network

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3610 Disclosure of classes of share capital [table] Table

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ifrs-full:DisclosureOfClassesOfShareCapitalTable
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3612 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
3613 Ordinary Share Capital [member] Member ifrs-full:OrdinarySharesMember
3614 Three Hundred Million Preference Shares [member] Member ck0001087711:ThreeHundredMillionPreferenceSharesMember
3615 Disclosure of classes of share capital [line items] LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
3616 Number of shares issued and fully paid Concept (Shares) As Of ifrs-full:NumberOfSharesIssuedAndFullyPaid
3617 Issued and fully paid share capital Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
3618 1280 - Disclosure - Share Capital - Schedule of Share Capital Issued and Fully Paid (Parenthetical) (Detail) Network

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3619 Disclosure of classes of share capital [table] Table

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3622 Ordinary Share Capital [member] Member ifrs-full:OrdinarySharesMember
3623 Three Hundred Million Preference Shares [member] Member ck0001087711:ThreeHundredMillionPreferenceSharesMember
3624 Disclosure of classes of share capital [line items] LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
3625 Price per share Concept (Share) As Of ifrs-full:ParValuePerShare
3626 Notional amount Concept (Monetary) As Of ifrs-full:NotionalAmount
3627 1281 - Disclosure - Share Capital - Summary of Share Premium (Detail) Network

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3628 Implied Table Table

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3630 Share premium Concept (Monetary) As Of Credit ifrs-full:SharePremium
3631 1282 - Disclosure - Share Capital - Additional Information (Detail) Network

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3632 Disclosure of classes of share capital [table] Table

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*

ifrs-full:DisclosureOfClassesOfShareCapitalTable
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3634 Equity [member] Member ifrs-full:EquityMember
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3636 Disclosure of classes of share capital [line items] LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
3637 Sterling preference shares, Notional amount Concept (Monetary) As Of ck0001087711:SterlingPreferenceSharesNotionalAmount
3638 Notional amount Concept (Monetary) As Of ifrs-full:NotionalAmount
3639 Fixed non-cumulative annual dividend payable percentage Concept (Percent) For Period ck0001087711:FixedNoncumulativeAnnualDividendPayablePercentage
3640 Fixed non-cumulative quarterly dividend payable percentage Concept (Percent) For Period ck0001087711:FixedNoncumulativeQuarterlyDividendPayablePercentage
3641 1283 - Disclosure - Other Equity Instruments - Summary of Other Equity Instruments (Detail) Network

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3642 Disclosure of other equity instruments [table] Table

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ck0001087711:DisclosureOfOtherEquityInstrumentsTable
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3644 Equity [member] Member ifrs-full:EquityMember
3645 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001087711:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3646 500m Perpetual Capital Securities [member] Member ck0001087711:FiveHundredMillionPerpetualCapitalSecuritiesTwoThousandTwentyFourMember
3647 750m Perpetual Capital Securities [member] Member ck0001087711:SevenHundredAndFiftyMillionPerpetualCapitalSecuritiesMember
3648 300m Perpetual Capital Securities [member] Member ck0001087711:ThreeHundredMillionPerpetualCapitalSecuritiesMember
3649 500m Perpetual Capital Securities [member] Member ck0001087711:FiveHundredMillionPerpetualCapitalSecuritiesMember
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3651 Initial interest rate Concept (Percent) For Period ck0001087711:PercentageOnOtherEquityInterest
3652 First call date Concept (Year/Month) For Period ck0001087711:OtherEquityInterestMaturityPeriod
3653 Other equity instruments Concept (Monetary) As Of Credit ifrs-full:OtherEquityInterest
3654 1284 - Disclosure - Other Equity Instruments - Additional Information (Detail) Network

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3655 Disclosure of other equity instruments [table] Table

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ck0001087711:DisclosureOfOtherEquityInstrumentsTable
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3657 Equity [member] Member ifrs-full:EquityMember
3658 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001087711:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3659 500m Fixed Rate Reset Perpetual AT1 Capital Securities [member] Member ck0001087711:FiveHundredMillionFixedRateResetPerpetualATOneCapitalSecuritiesMember
3660 6.475 % Perpetual Capital Securities [member] Member ck0001087711:SixPointFourSevenFivePercentagePerpetualCapitalSecuritiesMember
3661 Disclosure of other equity instruments [line items] LineItems ck0001087711:DisclosureOfOtherEquityInstrumentsLineItems
3662 Reserve Capital Instruments bear interest rate reset period Concept (xbrli:durationItemType) For Period ck0001087711:StepUpCallablePerpetualReserveCapitalInstrumentsBearInterestRateResetPeriod
3663 Reserve Capital Instruments benchmark gilt rate period Concept (xbrli:durationItemType) For Period ck0001087711:StepUpCallablePerpetualReserveCapitalInstrumentsBearInterestRateGiltRateBenchmarkPeriod
3664 Common equity tier 1 capital ratio minimum Concept (Percent) For Period ck0001087711:CommonEquityTierOneCapitalRatioMinimum
3665 Distribution rate resets, period Concept (xbrli:durationItemType) For Period ck0001087711:DistributionRateResetsBasedOnPrevailingFiveYearSterlingMidSwapRatePeriod
3666 Capital securities purchased and redeemed Concept (Percent) For Period ck0001087711:PercentageOfCapitalSecuritiesPurchasedAndRedeemed
3667 1285 - Disclosure - Other Equity Instruments - Summary of Other Equity Instruments (Parenthetical) (Detail) Network

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3668 Disclosure of other equity instruments [table] Table

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ck0001087711:DisclosureOfOtherEquityInstrumentsTable
3669 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3670 Equity [member] Member ifrs-full:EquityMember
3671 300m Step-up Callable Perpetual Reserve Capital Instruments [member] Member ck0001087711:ThreeHundredMillionStepupCallablePerpetualReserveCapitalInstrumentsMember
3672 500m Perpetual Capital Securities [member] Member ck0001087711:FiveHundredMillionPerpetualCapitalSecuritiesTwoThousandTwentyFourMember
3673 750m Perpetual Capital Securities [member] Member ck0001087711:SevenHundredAndFiftyMillionPerpetualCapitalSecuritiesMember
3674 300m Perpetual Capital Securities [member] Member ck0001087711:ThreeHundredMillionPerpetualCapitalSecuritiesMember
3675 500m Perpetual Capital Securities [member] Member ck0001087711:FiveHundredMillionPerpetualCapitalSecuritiesMember
3676 Disclosure of other equity instruments [line items] LineItems ck0001087711:DisclosureOfOtherEquityInstrumentsLineItems
3677 Capital securities Concept (Monetary) For Period Credit ck0001087711:CapitalSecuritiesIssued
3678 1286 - Disclosure - Non-Controlling Interests - Schedule of Amounts Attributable to Non-Controlling Interests (Detail) Network

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3679 Disclosure of Non-controlling Interests [table] Table

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ck0001087711:DisclosureOfNoncontrollingInterestsTable
3680 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
3681 Equity [member] Member ifrs-full:EquityMember
3682 PSA Finance UK Limited [member] Member ck0001087711:PSAFinanceUKLimitedMember
3683 Disclosure of noncontrolling interests [line items] LineItems ck0001087711:DisclosureOfNoncontrollingInterestsLineItems
3684 Non-controlling interests Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
3685 1287 - Disclosure - Changes in Liabilities Arising From Financing Activities - Summary of Changes in Liabilities Arising from Financing Activities (Detail) Network

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3686 Disclosure of reconciliation of liabilities arising from financing activities [table] Table

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ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesTable
3687 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3688 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3689 Debt Securities [member] Member ck0001087711:DebtSecuritiesInIssueMember
3690 Subordinated liabilities [member] Member ck0001087711:SubordinatedLiabilitiesMember
3691 Other Equity Instruments [member] Member ifrs-full:OtherEquityInterestMember
3692 Dividends Paid [member] Member ck0001087711:DividendsPaidMember
3693 Disclosure of reconciliation of liabilities arising from financing activities [line items] LineItems ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesLineItems
3694 Beginning Balance Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
3695 Cash flows from financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
3696 Cash flows from operating activities Concept (Monetary) For Period ck0001087711:CashFlowsFromUsedInOperatingActivitiesArisingFromChangeInLiabilitiesOfFinancing
3697 - Unrealised foreign exchange Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughEffectOfChangesInForeignExchangeRatesLiabilitiesArisingFromFinancingActivities
3698 - Other changes Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughOtherChangesLiabilitiesArisingFromFinancingActivities
3699 Ending Balance Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
3700 1288 - 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

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3701 Disclosure of assets pledged as security [table] Table

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ck0001087711:DisclosureOfAssetsPledgedAsSecurityTable
3702 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
3703 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
3704 On-Balance Sheet [member] Member ck0001087711:OnBalanceSheetMember
3705 Off-Balance Sheet [member] Member ck0001087711:OffBalanceSheetMember
3706 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3707 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3708 Cash and Balances at Central Banks [member] Member ck0001087711:CashAndBalancesWithCentralBanksMember
3709 Trading Assets [member] Member ck0001087711:TradingAssetsMember
3710 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
3711 Loans and advances to banks [member] Member ck0001087711:LoansAndAdvancesToBanksMember
3712 Other financial assets at amortised cost [member] Member ck0001087711:OtherFinancialAssetsAtAmortisedCostMember
3713 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
3714 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
3715 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3716 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3717 Securitisations and Covered Bonds [member] Member ck0001087711:SecuritisationsAndCoveredBondsMember
3718 Other [member] Member ck0001087711:OtherMember
3719 Disclosure of assets pledged as security [line items] LineItems ck0001087711:DisclosureOfAssetsPledgedAsSecurityLineItems
3720 Assets charged as security for liabilities Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
3721 1289 - Disclosure - Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Additional Information (Detail) Network

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3722 Disclosure of assets pledged as security [table] Table

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*

ck0001087711:DisclosureOfAssetsPledgedAsSecurityTable
3723 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3724 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3725 Fellow Subsidiaries [member] Member ifrs-full:SubsidiariesMember
3726 Santander UK Plc [member] Member ck0001087711:SantanderUkPlcMember
3727 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3728 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3729 Sale and Repurchase Agreements [member] Member ck0001087711:SaleAndRepurchaseAgreementsMember
3730 Loans and advances to customers- securitisations and covered bonds [member] Member ck0001087711:LoansAndAdvancesToCustomersSecuritisationsAndCoveredBondsMember
3731 Internally Retained [member] Member ck0001087711:InternallyRetainedMember
3732 Third Party Bilateral Secured Funding Transactions [member] Member ck0001087711:ThirdPartyBilateralSecuredFundingTransactionsMember
3733 Cash [member] Member ck0001087711:Cash1Member
3734 Purchase and resale agreements [member] Member ck0001087711:PurchaseAndResaleAgreementsMember
3735 Continuing involvement in derecognised financial assets by type of transfer [axis] Axis ifrs-full:ContinuingInvolvementInDerecognisedFinancialAssetsByTypeOfTransferAxis
3736 Types of transfer [member] Member ifrs-full:TypesOfTransferMember
3737 Securitisations and Covered Bonds [member] Member ck0001087711:SecuritisationsAndCoveredBondsMember
3738 Securities Lending [member] Member ifrs-full:SecuritiesLendingMember
3739 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3740 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3741 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
3742 Disclosure of assets pledged as security [line items] LineItems ck0001087711:DisclosureOfAssetsPledgedAsSecurityLineItems
3743 Assets charged as security for liabilities Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
3744 Gross assets charged as security for liabilities Concept (Monetary) As Of Debit ifrs-full:AssetsRecognisedInEntitysFinancialStatementsInRelationToStructuredEntities
3745 Internally retained securitisation and covered bond issuances available for creating collateral Concept (Monetary) As Of Debit ck0001087711:NoteIssuancesAvailableForCreatingCollateral
3746 Notes issued under securitisation and covered bond programmes retained internally Concept (Monetary) As Of Credit ifrs-full:NotesAndDebenturesIssued
3747 Assets charged as security for liabilities Concept (Monetary) As Of Debit ck0001087711:AssetsPledgedAsCollateralForLiabilities
3748 Collateral accepted as security for assets Concept (Monetary) As Of Credit ck0001087711:CollateralAcceptedAsSecurityForAssets
3749 1290 - Disclosure - Assets Charged as Security for Liabilities and Collateral Accepted as Security for Assets - Schedule of Collateral Held as Security for Assets (Detail) Network

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3750 Disclosure of assets pledged as security [table] Table

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*

ck0001087711:DisclosureOfAssetsPledgedAsSecurityTable
3751 Assets and liabilities [axis] Axis ifrs-full:AssetsAndLiabilitiesAxis
3752 Assets and liabilities [member] Member ifrs-full:AssetsAndLiabilitiesMember
3753 On-Balance Sheet [member] Member ck0001087711:OnBalanceSheetMember
3754 Off-Balance Sheet [member] Member ck0001087711:OffBalanceSheetMember
3755 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3756 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3757 Trading Liabilities [member] Member ck0001087711:TradingLiabilities1Member
3758 Deposits by customers [member] Member ck0001087711:DepositsByCustomersMember
3759 Deposits by banks [member] Member ck0001087711:DepositsByBanksMember
3760 Disclosure of assets pledged as security [line items] LineItems ck0001087711:DisclosureOfAssetsPledgedAsSecurityLineItems
3761 Total on-balance sheet/ off-balance sheet Concept (Monetary) As Of Credit ck0001087711:CollateralAcceptedAsSecurityForAssets
3762 1291 - Disclosure - Share-Based Compensation - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureShareBasedCompensationAdditionalInformation
3763 Disclosure of terms and conditions of share-based payment arrangement [table] Table

*

*

ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
3764 Range [axis] Axis ifrs-full:RangeAxis
3765 Ranges [member] Member ifrs-full:RangesMember
3766 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3767 Top of Range [member] Member ifrs-full:TopOfRangeMember
3768 Variable Pay of Less Than 500,000 [member] Member ck0001087711:VariablePayOfLessThan500000Member
3769 Variable Pay at or Above 500,000 [member] Member ck0001087711:VariablePayAtOrAbove500000Member
3770 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3771 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3772 Long-Term Incentive Plan (LTIP) [member] Member ck0001087711:LongtermIncentivePlanMember
3773 Share Incentive Plans [member] Member ck0001087711:ShareIncentivePlansMember
3774 Regulatory deferral account balances [axis] Axis ifrs-full:RegulatoryDeferralAccountBalancesAxis
3775 Regulatory deferral account balances [member] Member ifrs-full:RegulatoryDeferralAccountBalancesMember
3776 Cash [member] Member ck0001087711:Cash1Member
3777 Shares [member] Member ck0001087711:SharesMember
3778 Title of individual 1 [axis] Axis ck0001087711:TitleOfIndividual1Axis
3779 Government Grants [domain] Member ck0001087711:GovernmentGrantsDomain
3780 Employees [member] Member ck0001087711:MaterialRiskTakersMember
3781 Disclosure of terms and conditions of share-based payment arrangement [line items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
3782 Liabilities arising from share-based payment transactions Concept (Monetary) As Of Credit ifrs-full:LiabilitiesFromSharebasedPaymentTransactions2011
3783 Liabilities arising from share-based payment transactions, vested liabilities Concept (Monetary) As Of Credit ifrs-full:IntrinsicValueOfLiabilitiesFromSharebasedPaymentTransactionsForWhichCounterpartysRightToCashOrOtherAssetsVested2011
3784 Number of sharesave schemes launched Concept (Integer) For Period ck0001087711:NumberOfSharesaveScehmesLaunched
3785 Year of grant of share-based payment arrangement Concept (Text/String) For Period ifrs-full:DateOfGrantOfSharebasedPaymentArrangement
3786 Employee saving on share based compensation Concept (Monetary) As Of Debit ck0001087711:EstimatedEmployeeSavingOnShareBasedCompensationPlan
3787 Terms of options Concept (xbrli:durationItemType) For Period ck0001087711:MaximumTermOfOptionsGrantedForShareBasedPaymentsArrangement
3788 Discount percent on share price under share based compensation plan Concept (Percent) For Period ck0001087711:EstimatedDiscountPercentOnSharePriceUnderShareBasedCompensationPlan
3789 Weighted average share price Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsInSharebasedPaymentArrangementExercisedDuringPeriodAtDateOfExercise
3790 Weighted average grant-date fair value Concept (Monetary) As Of Credit ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
3791 LTIP awarded Concept (Decimal) For Period ifrs-full:NumberOfInstrumentsOtherEquityInstrumentsGranted
3792 Percent of other equity instruments vested Concept (Percent) For Period ck0001087711:PercentOfOtherEquityInstrumentsVestedInSharebasedPaymentArrangement
3793 Annual bonus percentage Concept (Percent) For Period ck0001087711:AnnualBonusPercentage
3794 Deferred shares description Concept (Text/String) For Period ck0001087711:DeferredShareAwardsDescription
3795 Percentage of defer annual bonus Concept (Percent) For Period ck0001087711:PercentageOfDeferAnnualBonus
3796 Maximum investment value per tax year Concept (Monetary) As Of Debit ck0001087711:MaximumNetInvestmentValue
3797 Percentage of maximum salary that can be invested Concept (Percent) For Period ck0001087711:PercentageOfMaximumSalaryThatCanBeInvested
3798 Vesting requirements for sharebased payment arrangement Concept (Text/String) For Period ifrs-full:DescriptionOfVestingRequirementsForSharebasedPaymentArrangement
3799 Number of shares outstanding Concept (Shares) For Period ifrs-full:IncreaseDecreaseInNumberOfSharesOutstanding
3800 1292 - Disclosure - Share-Based Compensation - Summary of Movement in Share Options (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureShareBasedCompensationSummaryOfMovementInShareOptions
3801 Disclosure of terms and conditions of share-based payment arrangement [table] Table

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ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
3802 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3803 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3804 Sharesave Schemes [member] Member ck0001087711:SharesaveSchemesMember
3805 Disclosure of terms and conditions of share-based payment arrangement [line items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
3806 Number of options outstanding beginning balance Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
3807 Number of options granted Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
3808 Number of options exercised Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
3809 Number of options forfeited/expired Concept (Decimal) For Period ck0001087711:NumberOfShareOptionsForfeitedOrExpiredInSharebasedPaymentArrangement
3810 Number of options transferred to SEIL Concept (Decimal) For Period ck0001087711:NumberOfShareOptionsTransferredToSEIL
3811 Number of options outstanding ending balance Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
3812 Number of options exercisable Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
3813 Weighted average exercise price outstanding beginning balance Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
3814 Weighted average exercise price granted Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsGrantedInSharebasedPaymentArrangement
3815 Weighted average exercise price exercised Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisedInSharebasedPaymentArrangement
3816 Weighted average exercise price forfeited/expired Concept (Monetary) For Period ck0001087711:WeightedAverageExercisePriceOfShareOptionsForfeitedOrExpiredInSharebasedPaymentArrangement
3817 Weighted average exercise price transferred to SEIL Concept (Monetary) For Period ck0001087711:WeightedAverageExercisePriceOfShareOptionsTransferredToSEILInSharebasedPaymentArrangement
3818 Weighted average exercise price outstanding ending balance Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
3819 Weighted average exercise price exercisable ending balance Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
3820 1293 - Disclosure - Share-Based Compensation - Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding (Detail) Network

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3821 Disclosure of number and weighted average remaining contractual life of outstanding share options [table] Table

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ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsTable
3822 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3823 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3824 Sharesave Schemes [member] Member ck0001087711:SharesaveSchemesMember
3825 Ranges of exercise prices for outstanding share options [axis] Axis ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsAxis
3826 Ranges of exercise prices for outstanding share options [member] Member ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsMember
3827 2 to 3 [member] Member ck0001087711:PoundTwoToPoundThreeMember
3828 3 to 4 [member] Member ck0001087711:PoundThreeToPoundFourMember
3829 4 to 5 [member] Member ck0001087711:PoundFourToPoundFiveMember
3830 Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] LineItems ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsLineItems
3831 Options outstanding , Weighted average remaining contractual life years Concept (xbrli:durationItemType) For Period ck0001087711:WeightedAveragesRemainingContractualLifeOfOutstandingShareOptions
3832 Option outstanding, Weighted average exercise price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
3833 1294 - Disclosure - Share-Based Compensation - Summary of Range of Exercise Prices and Weighted Average Remaining Contractual Life of the Options Outstanding (Parenthetical) (Detail) Network

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3834 Disclosure of number and weighted average remaining contractual life of outstanding share options [table] Table

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ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsTable
3835 Ranges of exercise prices for outstanding share options [axis] Axis ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsAxis
3836 Ranges of exercise prices for outstanding share options [member] Member ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsMember
3837 2 to 3 [member] Member ck0001087711:PoundTwoToPoundThreeMember
3838 3 to 4 [member] Member ck0001087711:PoundThreeToPoundFourMember
3839 4 to 5 [member] Member ck0001087711:PoundFourToPoundFiveMember
3840 Range [axis] Axis ifrs-full:RangeAxis
3841 Ranges [member] Member ifrs-full:RangesMember
3842 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
3843 Top of Range [member] Member ifrs-full:TopOfRangeMember
3844 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3845 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3846 Sharesave Schemes [member] Member ck0001087711:SharesaveSchemesMember
3847 Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] LineItems ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsLineItems
3848 Range of exercise prices Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
3849 1295 - Disclosure - Share-Based Compensation - Summary of Movement in Value of Conditional Awards in LTIPs (Detail) Network

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3850 Disclosure of terms and conditions of share-based payment arrangement [table] Table

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*

ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
3851 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
3852 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
3853 2015 LTIP [member] Member ck0001087711:TwoThousandAndFifteenLongTermIncentivePlanMember
3854 2014 LTIP [member] Member ck0001087711:TwoThousandAndFourteenLongTermIncentivePlanMember
3855 Disclosure of terms and conditions of share-based payment arrangement [line items] LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
3856 Conditional awards at the beginning of the year Concept (Monetary) As Of Credit ck0001087711:ConditionalAwards
3857 Conditional awards forfeited or cancelled Concept (Monetary) For Period Debit ck0001087711:ConditionalAwardsForfeitedOrCancelled
3858 Conditional awards outstanding at the end of the year Concept (Monetary) As Of Credit ck0001087711:ConditionalAwards
3859 1296 - Disclosure - Transactions With Directors and Other Key Management Personnel - Summary of Remuneration of the Directors and Other Key Management Personnel (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureTransactionsWithDirectorsAndOtherKeyManagementPersonnelSummaryOfRemunerationOfTheDirectorsAndOtherKeyManagementPersonnel
3860 Implied Table Table

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implied:Table
3861 Disclosure Of Remuneration Of Directors And Other Key Management Personnel [abstract] Abstract ck0001087711:DisclosureOfRemunerationOfDirectorsAndOtherKeyManagementPersonnelAbstract
3862 Salaries and fees Concept (Monetary) For Period Debit ck0001087711:DirectorsSalariesAndFees
3863 Performance-related payments Concept (Monetary) For Period Debit ck0001087711:DirectorsPerformanceRelatedPayments
3864 Other fixed remuneration (pension and other allowances & non-cash benefits) Concept (Monetary) For Period Debit ck0001087711:DirectorsExpenses
3865 Expenses Concept (Monetary) For Period Debit ifrs-full:DirectorsRemunerationExpense
3866 Total remuneration Concept (Monetary) For Period Debit ck0001087711:DirectorsRemuneration
3867 Short-term employee benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationShorttermEmployeeBenefits
3868 Post-employment benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationPostemploymentBenefits
3869 Total compensation Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensation
3870 1297 - Disclosure - Transactions With Directors and Other Key Management Personnel - Summary of Remuneration of the Directors and Other Key Management Personnel (Parenthetical) (Detail) Network

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3871 Disclosure Of Directors And Key Management Remuneration [table] Table

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ck0001087711:DisclosureOfDirectorsAndKeyManagementRemunerationTable
3872 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
3873 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
3874 Banco Santander SA London Branch [member] Member ck0001087711:BancoSantanderSALondonBranchMember
3875 Disclosure of directors and key management remuneration [line items] LineItems ck0001087711:DisclosureOfDirectorsAndKeyManagementRemunerationLineItems
3876 Number of shares made as buy-outs of deferred performance-related payment Concept (Shares) For Period ck0001087711:DeferredPerformanceRelatedNumberOfShares
3877 Payments made as buy-outs of deferred performance-related payment Concept (Monetary) For Period Debit ck0001087711:DeferredPerformanceRelatedPayments
3878 Number of previously employed individuals for buy-out of deferred performance related payment Concept (Integer) For Period ck0001087711:NumberOfPreviouslyEmployedIndividualsForBuyoutsOfDeferredPerformanceRelatedPayments
3879 Termination payment Concept (Monetary) For Period Debit ifrs-full:TerminationBenefitsExpense
3880 Number key management persons who receives termination benefit Concept (Integer) For Period ck0001087711:NumberOfKeyManagementPersonnelWhoReceiveTerminationBenefit
3881 1298 - Disclosure - Transactions With Directors and Other Key Management Personnel - Additional Information (Detail) Network

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3882 Disclosure Of Directors And Key Management Remuneration [table] Table

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ck0001087711:DisclosureOfDirectorsAndKeyManagementRemunerationTable
3883 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3884 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3885 Banco Santander SA [member] Member ck0001087711:BancoSantanderSAMember
3886 Other key management personnel [member] Member ck0001087711:OtherKeyManagementPersonnelMember
3887 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
3888 Remuneration excluding pension contribution Concept (Monetary) For Period Credit ck0001087711:DirectorsRemunerationExpenseHighestPaidDirector
3889 Remuneration excluding pension contribution performance related Concept (Monetary) For Period Debit ck0001087711:RemunerationExcludingPensionContributionPerformanceRelatedHighestPaidDirector
3890 Deferred pension benefit accruing under a defined benefit scheme Concept (Monetary) For Period Debit ck0001087711:DeferredPensionBenefitAccruingUnderDefinedBenefitScheme
3891 Ex gratia pensions paid to former Directors Concept (Monetary) For Period Debit ck0001087711:ExgratiaPensionsPaid
3892 Directors who held any interest in the shares Concept (Integer) For Period ck0001087711:NumberOfDirectorsWhoHeldInterestInShares
3893 Directors who exercised or were granted any rights to subscribe for shares Concept (Integer) For Period ck0001087711:NumberOfDirectorsWhoExercisedOrWereGrantedAnyRightsToSubscribeForShares
3894 Loans made to directors Concept (Monetary) For Period Credit ck0001087711:DirectorsLoansPrincipalAmountOutstanding
3895 Number of loan made to directors Concept (Integer) For Period ck0001087711:NumberOfLoansMadeToDirectors
3896 Benefits paid in kind for directors Concept (Monetary) For Period Debit ifrs-full:DirectorsRemunerationExpense
3897 Number of directors paid in kind Concept (Integer) For Period ck0001087711:NumberOfDirectors
3898 Benefits paid in kind for key management Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensation
3899 Number of key management paid in kind Concept (Integer) For Period ck0001087711:NumberOfKeyManagementPersonnel
3900 Loans made to key management personnel Concept (Monetary) For Period Credit ifrs-full:CashAdvancesAndLoansMadeToRelatedParties
3901 Number of loan made to key management personnel Concept (Integer) For Period ck0001087711:NumberOfLoansMadeToKeyManagementPersonnel
3902 1299 - Disclosure - Transactions With Directors and Other Key Management Personnel - Summary of Transactions with Directors, Other Key Management Personnel (Detail) Network

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3903 Disclosure Of Directors And Key Management Remuneration [table] Table

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ck0001087711:DisclosureOfDirectorsAndKeyManagementRemunerationTable
3904 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3905 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3906 Key management personnel of entity or parent [member] Member ifrs-full:KeyManagementPersonnelOfEntityOrParentMember
3907 Disclosure of directors and key management remuneration [line items] LineItems ck0001087711:DisclosureOfDirectorsAndKeyManagementRemunerationLineItems
3908 Number of secured loans, unsecured loans and overdrafts, beginning balance Concept (Integer) As Of ck0001087711:NumberOfSecuredLoansUnsecuredLoansAndOverdrafts
3909 Number of secured loans, unsecured loans and overdrafts, net movements Concept (Integer) For Period ck0001087711:NumberOfSecuredLoansUnsecuredLoansAndOverdraftsNetMovement
3910 Number of secured loans, unsecured loans and overdrafts, ending balance Concept (Integer) As Of ck0001087711:NumberOfSecuredLoansUnsecuredLoansAndOverdrafts
3911 Beginning balance Concept (Monetary) As Of Credit ck0001087711:SecuredLoansUnsecuredLoansAndOverdrafts
3912 Net movements Concept (Monetary) For Period Debit ck0001087711:SecuredLoansUnsecuredLoansAndOverdraftsNetMovements
3913 Ending balance Concept (Monetary) As Of Credit ck0001087711:SecuredLoansUnsecuredLoansAndOverdrafts
3914 Number of deposit, bank and instant access accounts and investments, beginning balance Concept (Integer) As Of ck0001087711:NumberOfDepositBankAndInstantAccessAccountsAndInvestments
3915 Number of deposit, bank and instant access accounts and investments, net movements Concept (Integer) For Period ck0001087711:NumberOfDepositBankAndInstantAccessAccountsAndInvestmentsNetMovement
3916 Number of deposit, bank and instant access accounts and investments, ending balance Concept (Integer) As Of ck0001087711:NumberOfDepositBankAndInstantAccessAccountsAndInvestments
3917 Beginning balance Concept (Monetary) As Of Credit ck0001087711:DepositBankAndInstantAccessAccountsAndInvestments
3918 Net movements Concept (Monetary) For Period Debit ck0001087711:DepositBankAndInstantAccessAccountsAndInvestmentsNetMovement
3919 Ending balance Concept (Monetary) As Of Credit ck0001087711:DepositBankAndInstantAccessAccountsAndInvestments
3920 1300 - Disclosure - Related Party Disclosures - Summary of Transactions With Related Parties (Detail) Network

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3921 Disclosure of transactions between related parties [table] Table

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ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
3922 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3923 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3924 Ultimate Parent [Member] Member ck0001087711:UltimateParentMember
3925 Immediate Parent [member] Member ck0001087711:ImmediateParentMember
3926 Fellow Subsidiaries [member] Member ifrs-full:SubsidiariesMember
3927 Associates and Joint Ventures [Member] Member ck0001087711:AssociatesAndJointVenturesMember
3928 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
3929 Interest, fees and other income received Concept (Monetary) For Period Credit ck0001087711:InterestFeesAndOtherIncomeReceived
3930 Interest, fees and other expenses paid Concept (Monetary) For Period Debit ck0001087711:InterestFeesAndOtherExpensePaid
3931 Amounts owed by related parties Concept (Monetary) As Of Debit ifrs-full:AmountsReceivableRelatedPartyTransactions
3932 Amounts owed to related parties Concept (Monetary) As Of Credit ifrs-full:AmountsPayableRelatedPartyTransactions
3933 1301 - Disclosure - Related Party Disclosures - Additional Information (Detail) Network

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3934 Disclosure of transactions between related parties [table] Table

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ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
3935 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
3936 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
3937 Banco Santander London Branch [member] Member ck0001087711:BancoSantanderLondonBranchMember
3938 Santander UK Group Holdings plc [member] Member ck0001087711:SantanderUkGroupHoldingsPlcMember
3939 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3940 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3941 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
3942 Disclosure of transactions between related parties [line items] LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
3943 Customer loans Concept (Monetary) As Of Debit ifrs-full:ConsumerLoans
3944 Other assets Concept (Monetary) As Of Debit ifrs-full:OtherAssets
3945 Liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
3946 Decrease in RWAs due to transfers Concept (Monetary) For Period Debit ck0001087711:DecreaseInRiskweightedAssetsDueToModelChanges
3947 Dividend paid Concept (Monetary) For Period Debit ifrs-full:DividendsPaid
3948 Percentage of sale of share capital in subsidiaries Concept (Percent) For Period ck0001087711:SaleOfShareCapitalIssuedPercentage
3949 Cash consideration Concept (Monetary) For Period Credit ifrs-full:ConsiderationPaidReceived
3950 1302 - Disclosure - Financial Instruments - Analysis of Fair Value of Financial Instruments Carried at Amortised (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsAnalysisOfFairValueOfFinancialInstrumentsCarriedAtAmortised
3951 Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [table] Table

*

*

ck0001087711:DisclosureOfFairValuesOfFinancialInstrumentsCarriedAtAmortisedCostTable
3952 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
3953 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
3954 Level 1 [member] Member ifrs-full:Level1OfFairValueHierarchyMember
3955 Level 2 [member] Member ifrs-full:Level2OfFairValueHierarchyMember
3956 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
3957 Fair Value [member] Member ifrs-full:AtFairValueMember
3958 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
3959 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
3960 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
3961 Loans and advances to banks [member] Member ck0001087711:LoansAndAdvancesToBanksMember
3962 Reverse repurchase agreements - non-trading [member] Member ck0001087711:ReverseRepurchaseAgreementsNontradingMember
3963 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
3964 Categories of financial liabilities [axis] Axis ifrs-full:CategoriesOfFinancialLiabilitiesAxis
3965 Financial liabilities, category [member] Member ifrs-full:FinancialLiabilitiesCategoryMember
3966 Deposits by customers [member] Member ck0001087711:DepositsByCustomersMember
3967 Deposits by banks [member] Member ck0001087711:DepositsByBanksMember
3968 Repurchase agreements - non trading [member] Member ck0001087711:RepurchaseAgreementsNontradingMember
3969 Debt Securities [member] Member ck0001087711:DebtSecuritiesInIssueMember
3970 Subordinated liabilities [member] Member ck0001087711:SubordinatedLiabilitiesMember
3971 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
3972 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
3973 Financial Liabilities at Amortised Cost, Category [member] Member ifrs-full:FinancialLiabilitiesAtAmortisedCostCategoryMember
3974 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
3975 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
3976 Financial assets at amortised cost [member] Member ifrs-full:FinancialAssetsAtAmortisedCostMember
3977 Disclosure Of Fair Values Of Financial Instruments Carried At Amortised Cost [line items] LineItems ck0001087711:DisclosureOfFairValuesOfFinancialInstrumentsCarriedAtAmortisedCostLineItems
3978 Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
3979 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
3980 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
3981 Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
3982 Financial investments Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
3983 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
3984 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
3985 Loans and advances to banks Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToBanks
3986 Reverse repurchase agreements - non trading Concept (Monetary) As Of Debit ifrs-full:ReverseRepurchaseAgreementsAndCashCollateralOnSecuritiesBorrowed
3987 Other financial assets at amortised cost Concept (Monetary) As Of Debit ck0001087711:OtherFinancialAssetsAtAmortisedCost
3988 Financial investments Concept (Monetary) As Of Debit ck0001087711:FinancialInvestments
3989 Financial assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
3990 1303 - Disclosure - Financial Instruments - Fair Values of Financial Instruments Measured at Fair Value on a Recurring Basis (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsFairValuesOfFinancialInstrumentsMeasuredAtFairValueOnARecurringBasis
3991 Disclosure of fair value measurement of assets [table] Table

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*

ifrs-full:DisclosureOfFairValueMeasurementOfAssetsTable
3992 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
3993 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
3994 Securities Purchased Under Resale Agreements [member] Member ck0001087711:SecuritiesPurchasedUnderResaleAgreementsMember
3995 Debt Securities [member] Member ifrs-full:DebtSecuritiesMember
3996 Equity securities [member] Member ifrs-full:TradingEquitySecuritiesMember
3997 Cash Collateral [member] Member ck0001087711:CashCollateralMember
3998 Short-term loans [member] Member ck0001087711:ShortTermLoansMember
3999 Exchange Rate Contracts [member] Member ck0001087711:ExchangeRateContractsMember
4000 Interest Rate Contracts [member] Member ifrs-full:InterestRateSwapContractMember
4001 Equity and Credit Contracts [member] Member ck0001087711:EquityAndCreditContractsMember
4002 Netting [member] Member ck0001087711:NettingContractsMember
4003 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
4004 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
4005 Reverse repurchase agreements - non-trading [member] Member ck0001087711:ReverseRepurchaseAgreementsNontradingMember
4006 Available for sale debt securities [member] Member ck0001087711:AvailableForSaleDebtSecuritiesMember
4007 Available for sale equity securities [member] Member ck0001087711:AvailableForSaleEquitySecuritiesMember
4008 Securities Sold Under Repurchase Agreements [member] Member ck0001087711:SecuritiesSoldUnderRepurchaseAgreementsMember
4009 Short Positions in Securities and Unsettled Trades [member] Member ck0001087711:ShortPositionsInSecuritiesAndUnsettledTradesMember
4010 Short-term Deposits [member] Member ck0001087711:ShortTermDepositsMember
4011 Debt Securities [member] Member ck0001087711:DebtSecuritiesInIssueMember
4012 Structured Deposits [member] Member ck0001087711:StructuredDepositsMember
4013 Collateral and associated financial guarantees [member] Member ck0001087711:CollateralsAndGuaranteesMember
4014 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4015 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4016 Level 1 [member] Member ifrs-full:Level1OfFairValueHierarchyMember
4017 Level 2 [member] Member ifrs-full:Level2OfFairValueHierarchyMember
4018 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4019 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4020 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4021 Trading Assets [member] Member ck0001087711:TradingAssetsMember
4022 Derivative Financial Instruments [member] Member ck0001087711:DerivativeFinancialInstrumentsMember
4023 Other Financial assets at fair value through profit or loss, category [member] Member ck0001087711:OtherFinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
4024 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
4025 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
4026 Categories of financial liabilities [axis] Axis ifrs-full:CategoriesOfFinancialLiabilitiesAxis
4027 Financial liabilities, category [member] Member ifrs-full:FinancialLiabilitiesCategoryMember
4028 Trading Liabilities [member] Member ck0001087711:TradingLiabilities1Member
4029 Derivative Financial Instruments [member] Member ck0001087711:DerivativeFinancialInstrumentsMember
4030 Other financial liabilities designated at fair value through profit or loss [member] Member ck0001087711:OtherFinancialLiabilitiesDesignatedAtFairValueThroughProfitOrLossMember
4031 Disclosure of fair value measurement of assets and liabilities [line items] LineItems ck0001087711:DisclosureOfFairValueMeasurementOfAssetsAndLiabilitiesLineItems
4032 Assets at fair value Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValue
4033 Valuation technique Concept (Text/String) For Period ck0001087711:FairValuesOfFinancialInstrumentsValuationTechniqueUsed
4034 Liabilities at fair value Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValue
4035 1304 - Disclosure - Financial Instruments - Additional Information (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformation
4036 Implied Table Table

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*

implied:Table
4037 Disclosure of financial assets [abstract] Abstract ifrs-full:DisclosureOfFinancialAssetsAbstract
4038 Fair value of financial instruments transferred from Level 1 to Level 2 Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel1IntoLevel2OfFairValueHierarchyAssets
4039 Fair value of financial instruments transferred from Level 2 to Level 1 Concept (Monetary) For Period ifrs-full:TransfersOutOfLevel2IntoLevel1OfFairValueHierarchyAssets
4040 Fair value of financial instruments transferred from Level 2 to Level 3, Derivative assets Concept (Monetary) For Period Debit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyAssets
4041 Fair value of financial instruments transferred from Level 2 to Level 3, Derivative liabilities Concept (Monetary) For Period Credit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyLiabilities
4042 Exposure to wrong-way risk Concept (Monetary) As Of Debit ck0001087711:ExposureToWrongWayRisk
4043 1305 - Disclosure - Financial Instruments - Summary of Fair Value Adjustment (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfFairValueAdjustment
4044 Disclosure of financial assets [table] Table

*

*

ifrs-full:DisclosureOfFinancialAssetsTable
4045 Fair Value Adjustments [axis] Axis ck0001087711:FairValueAdjustmentsAxis
4046 Fair Value Adjustments [domain] Member ck0001087711:FairValueAdjustmentsDomain
4047 Bid-Offer and Trade Specific Adjustments [Member] Member ck0001087711:BidOfferAndTradeSpecificRiskRelatedAdjustmentsMember
4048 Uncertainty [Member] Member ck0001087711:RiskRelatedUncertaintyAdjustmentsMember
4049 Credit Risk Adjustment [Member] Member ck0001087711:CreditRiskAdjustmentsMember
4050 Funding Fair Value Adjustment [Member] Member ck0001087711:RiskRelatedFundingFairValueAdjustmentMember
4051 Risk Related Adjustments [Member] Member ck0001087711:RiskRelatedAdjustmentsMember
4052 Model-Related [Member] Member ck0001087711:ModelRelatedAdjustmentsMember
4053 Day One Profit [Member] Member ck0001087711:DayOneProfitAdjustmentsMember
4054 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4055 Fair value adjustments Concept (Monetary) For Period Debit ck0001087711:FairValueAdjustmentsRisk
4056 1306 - Disclosure - Financial Instruments - Analysis of Financial Instruments Valued Using Internal Models Based on Information Other Than Market Data (Detail) Network

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*

http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsAnalysisOfFinancialInstrumentsValuedUsingInternalModelsBasedOnInformationOtherThanMarketData
4057 Disclosure of financial assets [table] Table

*

*

ifrs-full:DisclosureOfFinancialAssetsTable
4058 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4059 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4060 Reversionary property securities [member] Member ck0001087711:ReversionaryPropertyInterestsMember
4061 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
4062 Unlisted Equity Shares [member] Member ck0001087711:UnlistedEquitySharesMember
4063 Credit Linked Note [member] Member ck0001087711:CreditLinkedNoteMember
4064 Property Related Options and Forwards [Member] Member ck0001087711:PropertyRelatedOptionsAndForwardsMember
4065 Credit Protection Guarantees [member] Member ck0001087711:CreditProtectionGuaranteesMember
4066 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4067 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4068 Equity and Credit Contracts [member] Member ck0001087711:EquityAndCreditContractsMember
4069 Roll-up Mortgage Portfolio [member] Member ck0001087711:RollupMortgagePortfolioMember
4070 Debt Securities [member] Member ck0001087711:DebtSecuritiesInIssueMember
4071 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
4072 Other Loans [member] Member ck0001087711:OtherLoansMember
4073 Financial Guarantees [member] Member ck0001087711:FinancialGuaranteesMember
4074 Other Level 3 [member] Member ck0001087711:OtherLevelThreeMember
4075 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4076 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4077 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
4078 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4079 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4080 Derivative assets Concept (Monetary) As Of Debit ifrs-full:FinancialAssets
4081 FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
4082 FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
4083 Derivative liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
4084 FVTPL Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLoss
4085 Financial assets and liabilities Concept (Monetary) As Of Debit ck0001087711:FinancialAssetsAndLiabilities
4086 Other Level 3 assets Concept (Monetary) As Of Debit ifrs-full:OtherFinancialAssets
4087 Other Level 3 liabilities Concept (Monetary) As Of Credit ifrs-full:OtherFinancialLiabilities
4088 Total net assets Concept (Monetary) As Of Debit ifrs-full:NetAssetsLiabilities
4089 Financial asset liabilities Concept (Monetary) For Period Debit ck0001087711:GainsLossesRecognisedInProfitOrLossFairValueMeasurementAssetsLiabilities
4090 Derivative assets and other Level 3 assets, fair value movements recognised in profit/(loss) Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementAssets
4091 Derivative liabilities and other Level 3 liabilities, fair value movements recognised in profit/(loss) Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementLiabilities
4092 Total (expense)/income Concept (Monetary) For Period Debit ck0001087711:FairValueMovementRecognisedInProfitLoss
4093 1307 - Disclosure - Financial Instruments - Liabilities Reconciliation of Fair Value Measurements in Level 3 of the Fair Value Hierarchy (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsLiabilitiesReconciliationOfFairValueMeasurementsInLevel3OfTheFairValueHierarchy
4094 Disclosure of Financial Liabilities [Table] Table

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*

ifrs-full:DisclosureOfFinancialLiabilitiesTable
4095 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4096 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4097 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4098 Classes of liabilities [axis] Axis ifrs-full:ClassesOfLiabilitiesAxis
4099 Liabilities [member] Member ifrs-full:LiabilitiesMember
4100 Derivative Liabilities [Member] Member ck0001087711:DerivativeLiabilitiesMember
4101 Categories of financial liabilities [axis] Axis ifrs-full:CategoriesOfFinancialLiabilitiesAxis
4102 Financial liabilities, category [member] Member ifrs-full:FinancialLiabilitiesCategoryMember
4103 Fair Value Through P&L [member] Member ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossCategoryMember
4104 Financial Liabilities at Fair Value, Class [member] Member ifrs-full:FinancialLiabilitiesAtFairValueMember
4105 Disclosure of fair value measurement of liabilities [line items] LineItems ifrs-full:DisclosureOfFairValueMeasurementOfLiabilitiesLineItems
4106 Beginning balance Concept (Monetary) As Of Credit ifrs-full:Liabilities
4107 Adoption of IFRS 9 Concept (Monetary) For Period Credit ck0001087711:IncreaseDecreaseInFinancialLiabilities
4108 At 1 January 2018 Concept (Monetary) As Of Credit ck0001087711:LiabilitiesAfterAdoptionOfIFRS9
4109 Total (losses)/gains recognised in profit/loss, fair value movements Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementLiabilities
4110 Total (losses)/gains recognised in profit/loss, foreign exchange and other movements Concept (Monetary) For Period ck0001087711:GainsLossesRecognisedInProfitOrLossForeignExchangeAndOtherMovementsLiabilities
4111 Transfers in Concept (Monetary) For Period Credit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyLiabilities
4112 Gains recognised in other comprehensive income Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInOtherComprehensiveIncomeFairValueMeasurementLiabilities
4113 Additions Concept (Monetary) For Period Credit ifrs-full:PurchasesFairValueMeasurementLiabilities
4114 Sales Concept (Monetary) For Period Debit ifrs-full:SalesFairValueMeasurementLiabilities
4115 Settlements Concept (Monetary) For Period Debit ifrs-full:SettlementsFairValueMeasurementLiabilities
4116 Ending Balance Concept (Monetary) As Of Credit ifrs-full:Liabilities
4117 (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
4118 1308 - Disclosure - Financial Instruments - Assets Reconciliation of Fair Value Measurements in Level 3 of the Fair Value Hierarchy (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsAssetsReconciliationOfFairValueMeasurementsInLevel3OfTheFairValueHierarchy
4119 Disclosure of financial assets [table] Table

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*

ifrs-full:DisclosureOfFinancialAssetsTable
4120 Levels of fair value hierarchy [axis] Axis ifrs-full:LevelsOfFairValueHierarchyAxis
4121 All levels of fair value hierarchy [member] Member ifrs-full:AllLevelsOfFairValueHierarchyMember
4122 Level 3 [member] Member ifrs-full:Level3OfFairValueHierarchyMember
4123 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4124 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4125 Derivative Financial Instruments [member] Member ifrs-full:DerivativesMember
4126 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
4127 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4128 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4129 Fair Value Through P&L [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
4130 Financial assets at FVOCI [member] Member ck0001087711:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeMember
4131 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4132 Beginning balance Concept (Monetary) As Of Debit ifrs-full:Assets
4133 Adoption of IFRS 9 Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInFinancialAssets
4134 At 1 January 2018 Concept (Monetary) As Of Debit ck0001087711:AssetsAfterAdoptionOfIFRS9
4135 Total (losses)/gains recognised in profit/loss, fair value movements Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInProfitOrLossFairValueMeasurementAssets
4136 Total (losses)/gains recognised in profit/loss, foreign exchange and other movements Concept (Monetary) For Period ck0001087711:GainsLossesRecognisedInProfitOrLossForeignExchangeAndOtherMovementAssets
4137 Transfers in Concept (Monetary) For Period Debit ifrs-full:TransfersIntoLevel3OfFairValueHierarchyAssets
4138 Gains recognised in other comprehensive income Concept (Monetary) For Period ifrs-full:GainsLossesRecognisedInOtherComprehensiveIncomeFairValueMeasurementAssets
4139 Additions Concept (Monetary) For Period Debit ifrs-full:PurchasesFairValueMeasurementAssets
4140 Sales Concept (Monetary) For Period Credit ifrs-full:SalesFairValueMeasurementAssets
4141 Settlements Concept (Monetary) For Period Credit ifrs-full:SettlementsFairValueMeasurementAssets
4142 Ending Balance Concept (Monetary) As Of Debit ifrs-full:Assets
4143 (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
4144 1309 - Disclosure - Financial Instruments - Effects of Changes in Significant Unobservable Assumptions to Reasonably Possible Alternatives (Level 3) (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsEffectsOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevel3
4145 Effect of changes in significant unobservable assumptions to reasonably possible alternatives - Level 3 [table] Table

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ck0001087711:EffectOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevel3Table
4146 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4147 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4148 Fair Value Through P&L [Member] Member ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLossCategoryMember
4149 Financial assets at fair value through other comprehensive income [member] Member ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeCategoryMember
4150 Available-for-Sale [member] Member ck0001087711:AvailableForSaleMember
4151 Range [axis] Axis ifrs-full:RangeAxis
4152 Ranges [member] Member ifrs-full:RangesMember
4153 Bottom of Range [member] Member ifrs-full:BottomOfRangeMember
4154 Top of Range [member] Member ifrs-full:TopOfRangeMember
4155 Weighted average [member] Member ifrs-full:WeightedAverageMember
4156 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4157 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4158 Equity and Credit Contracts [member] Member ck0001087711:EquityAndCreditContractsMember
4159 Debt Securities [member] Member ck0001087711:DebtSecuritiesInIssueMember
4160 Equity Securities [member] Member ifrs-full:OtherEquitySecuritiesMember
4161 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
4162 Classes of financial liabilities [axis] Axis ifrs-full:ClassesOfFinancialLiabilitiesAxis
4163 Total [Member] Member ifrs-full:FinancialLiabilitiesMember
4164 Property Related Options and Forwards [Member] Member ck0001087711:PropertyRelatedOptionsAndForwardsMember
4165 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4166 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4167 Reversionary property securities [member] Member ck0001087711:ReversionaryPropertyInterestsMember
4168 Roll-up Mortgage Portfolio [member] Member ck0001087711:RollupMortgagePortfolioMember
4169 Unlisted Equity Shares [member] Member ck0001087711:UnlistedEquitySharesMember
4170 Other Loans [member] Member ck0001087711:OtherLoansMember
4171 Effect of changes in significant unobservable assumptions to reasonably possible alternatives - Level 3 [line items] LineItems ck0001087711:EffectOfChangesInSignificantUnobservableAssumptionsToReasonablyPossibleAlternativesLevel3LineItems
4172 Fair value Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValue
4173 Fair value Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValue
4174 Assumption description Concept (Text/String) For Period ifrs-full:ChangesInMethodsAndAssumptionsUsedInPreparingSensitivityAnalysis
4175 Assumption value Concept (Percent) For Period ck0001087711:InterestRateSignificantUnobservableInputs
4176 Shift Concept (Percent) For Period ck0001087711:ShiftInFairValueInstrument
4177 Favourable changes Concept (Monetary) For Period Credit ck0001087711:FavourableChangesInFairValue
4178 Unfavourable changes Concept (Monetary) For Period Credit ck0001087711:UnfavourableChangesInFairValue
4179 HPI spot rate index level Concept (Integer) For Period ck0001087711:HousePriceIndexSpotRateIndexLevel
4180 1310 - Disclosure - Financial Instruments - Maturities of Undiscounted Cash Flows for Financial Liabilities and Off Balance Sheet Commitments (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureFinancialInstrumentsMaturitiesOfUndiscountedCashFlowsForFinancialLiabilitiesAndOffBalanceSheetCommitments
4181 Disclosure Of Maturity Analysis For Financial Liabilities [table] Table

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ck0001087711:DisclosureOfMaturityAnalysisForFinancialLiabilitiesTable
4182 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4183 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4184 Undiscounted Cash Flow [member] Member ck0001087711:UndiscountedCashFlowMember
4185 Maturity [axis] Axis ifrs-full:MaturityAxis
4186 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
4187 On Demand [member] Member ifrs-full:OnDemandMember
4188 Not Later Than Three Months [member] Member ifrs-full:NotLaterThanThreeMonthsMember
4189 Later Than Three Months and Not Later Than One Year [member] Member ifrs-full:LaterThanThreeMonthsAndNotLaterThanOneYearMember
4190 Later Than One Year and Not Later Than Five Years [member] Member ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
4191 Later Than Five Years [member] Member ifrs-full:LaterThanFiveYearsMember
4192 Disclosure Of Maturity Analysis For Financial Liabilities [line items] LineItems ck0001087711:DisclosureOfMaturityAnalysisForFinancialLiabilitiesLineItems
4193 Trading liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilitiesAtFairValueThroughProfitOrLossClassifiedAsHeldForTrading
4194 Derivative financial instruments Concept (Monetary) As Of Credit ck0001087711:DerivativeFinancialLiabilitiesGross
4195 Other financial liabilities at fair value through profit or loss Concept (Monetary) As Of Credit ck0001087711:OtherFinancialLiabilitiesAtFairValueThroughProfitOrLoss
4196 Deposits by customers Concept (Monetary) As Of Credit ifrs-full:DepositsFromCustomers
4197 Deposits by banks Concept (Monetary) As Of Credit ifrs-full:DepositsFromBanks
4198 Repurchase agreements - non trading Concept (Monetary) As Of Credit ifrs-full:RepurchaseAgreementsAndCashCollateralOnSecuritiesLent
4199 Debt securities in issue Concept (Monetary) As Of Credit ifrs-full:DebtSecurities
4200 Subordinated liabilities Concept (Monetary) As Of Credit ifrs-full:SubordinatedLiabilities
4201 Financial liabilities Concept (Monetary) As Of Credit ifrs-full:FinancialLiabilities
4202 Off-balance sheet commitments given Concept (Monetary) As Of Credit ck0001087711:OffBalanceSheetCommitments
4203 1311 - Disclosure - Offsetting Financial Assets and Liabilities - Summary of Information about Impact of Offsetting of Financial Assets and Liabilities (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureOffsettingFinancialAssetsAndLiabilitiesSummaryOfInformationAboutImpactOfOffsettingOfFinancialAssetsAndLiabilities
4204 Disclosure Of Off Setting Of Financial Assets And Liabilities [table] Table

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ck0001087711:DisclosureOfOffSettingOfFinancialAssetsAndLiabilitiesTable
4205 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4206 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4207 Derivative Financial Liabilities [member] Member ck0001087711:DerivativeFinancialLiabilitiesMember
4208 Amortised cost [member] Member ck0001087711:AmortisedCostMember
4209 Fair Value [member] Member ifrs-full:AtFairValueMember
4210 Deposits by Customers and Banks [Member] Member ck0001087711:DepositsByCustomersAndBanksMember
4211 Derivative Financial Instruments [member] Member ck0001087711:DerivativeFinancialAssetsMember
4212 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
4213 Disclosure of offsetting of financial assets and liabilities [line items] LineItems ck0001087711:DisclosureOfOffSettingOfFinancialAssetsAndLiabilitiesLineItems
4214 Gross amounts, Assets Concept (Monetary) As Of Debit ifrs-full:GrossFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4215 Amounts offset, Assets Concept (Monetary) As Of Credit ifrs-full:GrossFinancialLiabilitiesSetOffAgainstFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4216 Net amounts reported on the balance sheet, Assets Concept (Monetary) As Of Debit ifrs-full:NetFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsInStatementOfFinancialPosition
4217 Financial instruments, Assets Concept (Monetary) As Of Credit ifrs-full:FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
4218 Financial collateral, Assets Concept (Monetary) As Of Credit ifrs-full:CashCollateralReceivedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
4219 Net amount, Assets Concept (Monetary) As Of Credit ifrs-full:AmountsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
4220 Assets not subject to enforceable netting arrangements, Assets Concept (Monetary) As Of Debit ck0001087711:AssetsNotSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4221 Balance sheet total, Assets Concept (Monetary) As Of Debit ifrs-full:NetFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4222 Gross amounts, Liabilities Concept (Monetary) As Of Credit ifrs-full:GrossFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4223 Amounts offset, Liabilities Concept (Monetary) As Of Debit ifrs-full:GrossFinancialAssetsSetOffAgainstFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4224 Net amounts reported on the balance sheet, Liabilities Concept (Monetary) As Of Credit ifrs-full:NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsInStatementOfFinancialPosition
4225 Financial instruments, Liabilities Concept (Monetary) As Of Debit ifrs-full:FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4226 Financial collateral, Liabilities Concept (Monetary) As Of Debit ifrs-full:CashCollateralPledgedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4227 Net amount, Liabilities Concept (Monetary) As Of Debit ifrs-full:AmountsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4228 Assets not subject to enforceable netting arrangements, Liabilities Concept (Monetary) As Of Credit ck0001087711:LiabilitiesNotSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilities
4229 Balance sheet total, Liabilities Concept (Monetary) As Of Credit ifrs-full:NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
4230 1312 - Disclosure - Ring-Fencing - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureRingFencingAdditionalInformation
4231 Implied Table Table

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implied:Table
4232 Disclosure of cost and expenses by nature [abstract] Abstract ck0001087711:DisclosureOfCostAndExpensesByNatureAbstract
4233 Total cost incurred in relation to compliance with ring-rencing legislation Concept (Monetary) For Period Debit ck0001087711:CostOfRingfencing
4234 1313 - 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

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureTransitionToIFRS9SummaryOfMeasurementCategoriesAndCarryingAmountsOfFinancialAssetsDeterminedInAccordanceWithIAS39AndIFRS9
4235 Transition to IFRS 9 [table] Table

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ck0001087711:TransitionToIFRS9Table
4236 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4237 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4238 IFRS 9 [member] Member ck0001087711:IFRS9Member
4239 IAS 39 [member] Member ck0001087711:InternationalAccountingStandardsThirtyNineMember
4240 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4241 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4242 Cash and Balances at Central Banks [member] Member ck0001087711:CashAndBalancesWithCentralBanksMember
4243 Trading Assets [member] Member ck0001087711:TradingAssetsMember
4244 Derivative Financial Instruments [member] Member ck0001087711:DerivativeFinancialAssetsMember
4245 Financial assets designated at fair value [member] Member ck0001087711:FinancialAssetsDesignatedAtFairValueMember
4246 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
4247 Loans and advances to banks [member] Member ck0001087711:LoansAndAdvancesToBanksMember
4248 Reverse repurchase agreements - non-trading [member] Member ck0001087711:ReverseRepurchaseAgreementsNontradingMember
4249 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
4250 Other Assets [member] Member ifrs-full:OtherAssetsMember
4251 Other financial assets designated at fair value through profit or loss [member] Member ck0001087711:OtherFinancialAssetsDesignatedAtFairValueThroughProfitOrLossMember
4252 Measurement [axis] Axis ifrs-full:MeasurementAxis
4253 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
4254 FVOCI [member] Member ck0001087711:FVOCIMember
4255 FVTPL [member] Member ck0001087711:FVTPLMember
4256 Amortised cost [member] Member ck0001087711:AmortisedCostMember
4257 FVTPL (Mandatory) [member] Member ck0001087711:FVTPLMandatoryMember
4258 FVTPL (Designated) [member] Member ck0001087711:FVTPLDesignatedMember
4259 Other financial assets at amortised cost [member] Member ck0001087711:OtherFinancialAssetsAtAmortisedCostMember
4260 Financial assets at FVOCI [member] Member ck0001087711:FinancialAssetsAtFairValueThroughOtherComprehensiveIncomeMember
4261 FVTPL (Mandatory)1 [member] Member ck0001087711:FVTPLMandatory1Member
4262 Amortised cost1 [member] Member ck0001087711:AmortisedCost1Member
4263 FVTPL (Mandatory)2 [member] Member ck0001087711:FVTPLMandatory2Member
4264 Loans and receivable securities [member] Member ck0001087711:LoansAndReceivablesMember
4265 FVTPL (Trading) [member] Member ck0001087711:FVTPLTradingMember
4266 FVTPL1 (Designated) [member] Member ck0001087711:FVTPLDesignated1Member
4267 FVTPL2 (Designated) [member] Member ck0001087711:FVTPLDesignated2Member
4268 Loans and receivable securities1 [member] Member ck0001087711:LoansAndReceivables1Member
4269 Loans and receivable securities2 [member] Member ck0001087711:LoansAndReceivables2Member
4270 Available for sale financial assets [member] Member ck0001087711:AvailableForSaleFinancialAssetsMember
4271 Available for sale financial assets1 [member] Member ck0001087711:AvailableForSaleFinancialAssets1Member
4272 Held to maturity investments [member] Member ck0001087711:HeldToMaturityInvestmentsMember
4273 Available for sale financial assets2 [member] Member ck0001087711:AvailableForSaleFinancialAssets2Member
4274 Transition to IFRS 9 [line items] LineItems ck0001087711:TransitionToIFRS9LineItems
4275 Re-classifications Concept (Monetary) As Of Debit ifrs-full:IncreaseDecreaseInFinancialAssetsArisingFromChangeInMeasurementAttributeFirstApplicationOfIFRS9
4276 Re-measurement Concept (Monetary) For Period Debit ck0001087711:AdjustmentForAdoptionOfIFRS9AllowanceAccountForCreditLossesOfFinancialAssets
4277 Ending balance before re-presentation Concept (Monetary) As Of Debit ck0001087711:AssetsBeforeRepresentation
4278 Re-presentation Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsCarryingAmountImmediatelyAfterInitialApplicationOfIFRS9
4279 Beginning balance Concept (Monetary) As Of Debit ifrs-full:Assets
4280 1314 - 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

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureTransitionToIFRS9SummaryOfMeasurementCategoriesAndCarryingAmountsOfFinancialAssetsDeterminedInAccordanceWithIAS39AndIFRS9Parenthetical
4281 Transition to IFRS 9 [table] Table

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ck0001087711:TransitionToIFRS9Table
4282 Categories of financial assets [axis] Axis ifrs-full:CategoriesOfFinancialAssetsAxis
4283 Financial assets, category [member] Member ifrs-full:FinancialAssetsCategoryMember
4284 Provisions for off-balance sheet exposures (IAS 37/IFRS 9) [member] Member ck0001087711:ProvisionsForOffbalanceSheetExposuresMember
4285 Classes of financial instruments [axis] Axis ifrs-full:ClassesOfFinancialInstrumentsAxis
4286 Financial instruments, class [member] Member ifrs-full:ClassesOfFinancialInstrumentsMember
4287 Financial guarantee contracts [member] Member ifrs-full:FinancialGuaranteeContractsMember
4288 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
4289 Assets [member] Member ifrs-full:ClassesOfAssetsMember
4290 Loans and Advances to Customers [member] Member ck0001087711:LoansAndAdvancesToCustomersMember
4291 Financial investments [member] Member ck0001087711:FinancialInvestmentsMember
4292 Legal entity [axis] Axis dei:LegalEntityAxis
4293 Entity [Domain] Member dei:EntityDomain
4294 Santander UK Group [member] Member ck0001087711:SantanderUKGroupMember
4295 Measurement [axis] Axis ifrs-full:MeasurementAxis
4296 Aggregated measurement [member] Member ifrs-full:AggregatedMeasurementMember
4297 FVOCI [member] Member ck0001087711:FVOCIMember
4298 FVTPL [member] Member ck0001087711:FVTPLMember
4299 Amortised cost [member] Member ck0001087711:AmortisedCostMember
4300 Available-for-Sale [member] Member ck0001087711:AvailableForSaleMember
4301 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4302 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4303 IFRS 9 [member] Member ck0001087711:IFRS9Member
4304 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
4305 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
4306 Allowance for credit losses [member] Member ifrs-full:AllowanceForCreditLossesMember
4307 Reclassifications [member] Member ck0001087711:ReclassificationsMember
4308 Remeasurements [member] Member ck0001087711:RemeasurementsMember
4309 Transition to IFRS 9 [line items] LineItems ck0001087711:TransitionToIFRS9LineItems
4310 Re-measurement Concept (Monetary) For Period Debit ck0001087711:AdjustmentForAdoptionOfIFRS9AllowanceAccountForCreditLossesOfFinancialAssets
4311 Increase in deferred tax asset Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInDeferredTaxLiabilityAsset
4312 Financial assets at FVOCI Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughOtherComprehensiveIncome
4313 Trading assets Concept (Monetary) As Of Debit ck0001087711:TradingAssets
4314 Financial assets at FVTPL Concept (Monetary) As Of Debit ifrs-full:FinancialAssetsAtFairValueThroughProfitOrLoss
4315 Downward remeasurement of loans and receivables Concept (Monetary) For Period Debit ck0001087711:DownwardRemeasurementOfLoansAndReceivables
4316 Downward remeasurement of financial asset Concept (Monetary) For Period Debit ck0001087711:DownwardRemeasurementOfFinancialAssets
4317 Loans and advances to customers Concept (Monetary) As Of Debit ifrs-full:LoansAndAdvancesToCustomers
4318 Other financial assets at FVTPL Concept (Monetary) As Of Debit ifrs-full:OtherFinancialAssets
4319 Financial investments Concept (Monetary) As Of Debit ck0001087711:FinancialInvestments
4320 1315 - Disclosure - Transition to IFRS 9 - Disclosure of Statutory Balance Sheet Reconciliation under IAS 39 and IFRS 9 (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureTransitionToIFRS9DisclosureOfStatutoryBalanceSheetReconciliationUnderIAS39AndIFRS9
4321 Disclosure of financial assets [table] Table

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ifrs-full:DisclosureOfFinancialAssetsTable
4322 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4323 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4324 IFRS 9 [member] Member ck0001087711:IFRS9Member
4325 Classes of financial assets [axis] Axis ifrs-full:ClassesOfFinancialAssetsAxis
4326 Financial assets, class [member] Member ifrs-full:FinancialAssetsMember
4327 Financial Assets at Amortised Cost, Category [member] Member ifrs-full:FinancialAssetsAtAmortisedCostCategoryMember
4328 Disclosure of financial assets [line items] LineItems ifrs-full:DisclosureOfFinancialAssetsLineItems
4329 To amortised cost from FVPTL Concept (Monetary) For Period Credit ifrs-full:GainLossArisingFromDerecognitionOfFinancialAssetsMeasuredAtAmortisedCost
4330 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
4331 1316 - Disclosure - Transition to IFRS 9 - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureTransitionToIFRS9AdditionalInformation
4332 Transition to IFRS 9 [table] Table

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ck0001087711:TransitionToIFRS9Table
4333 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
4334 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
4335 IFRS 9 [member] Member ck0001087711:IFRS9Member
4336 Transition to IFRS 9 [line items] LineItems ck0001087711:TransitionToIFRS9LineItems
4337 Effective interest rate Concept (Percent) As Of ifrs-full:EffectiveInterestRateOfFinancialAssetsReclassifiedOutOfFinancialAssetsAtFairValueThroughProfitOrLoss
4338 Interest income recognized Concept (Monetary) For Period Credit ifrs-full:InterestIncomeExpenseRecognisedForFinancialAssetsReclassifiedIntoMeasuredAtAmortisedCostFirstApplicationOfIFRS9
4339 1317 - Disclosure - Events After the Balance Sheet Date - Additional Information (Detail) Network

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http://imetrix.edgar-online.com/taxonomy/role/DisclosureEventsAfterTheBalanceSheetDateAdditionalInformation
4340 Implied Table Table

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implied:Table
4341 Disclosure of non-adjusting events after reporting period [abstract] Abstract ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodAbstract
4342 Description of nature of Non adjusting event after reporting period Concept (Text/String) For Period ifrs-full:DescriptionOfNatureOfNonadjustingEventAfterReportingPeriod
4343 Estimated investment to refurbish 100 branches Concept (Monetary) For Period Debit ck0001087711:EstimatedInvestmentToRefurbishBranchNetwork
4344 Number of branches being closed Concept (Integer) For Period ck0001087711:NumberOfBranchesBeingClosed
4345 Number of branches in our future branch network Concept (Integer) For Period ck0001087711:NumberOfBranchesInOurFutureBranchNetwork

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