STANTEC INC (SEC Filing Page | XBRL Cloud Viewer | XBRL Instance)

Line	Label	Object Class	Period Type	Balance	Report ElementName
1	1001 - Document - Document and Entity Information	Network	*	*	http://www.stantec.com/taxonomy/role/DocumentandEntityInformation
2	Implied Table	Table	*	*	implied:Table
3	Document - Document and Entity Information [Abstract]	Abstract			stn:DocumentandEntityInformationAbstract
4	Document Type	Concept (Submission Type)	For Period		dei:DocumentType
5	Amendment Flag	Concept (Yes/No)	For Period		dei:AmendmentFlag
6	Amendment Description	Concept (Text/String)	For Period		dei:AmendmentDescription
7	Document Period End Date	Concept (Date)	For Period		dei:DocumentPeriodEndDate
8	Document Fiscal Year Focus	Concept (Year)	For Period		dei:DocumentFiscalYearFocus
9	Document Fiscal Period Focus	Concept (Fiscal Period)	For Period		dei:DocumentFiscalPeriodFocus
10	Trading Symbol	Concept (Text/String)	For Period		dei:TradingSymbol
11	Entity Registrant Name	Concept (Text/String)	For Period		dei:EntityRegistrantName
12	Entity Central Index Key	Concept (CIK Number)	For Period		dei:EntityCentralIndexKey
13	Current Fiscal Year End Date	Concept (Month/Day)	For Period		dei:CurrentFiscalYearEndDate
14	Entity Current Reporting Status	Concept (Yes/No)	For Period		dei:EntityCurrentReportingStatus
15	Entity Emerging Growth Company	Concept (Yes/No)	For Period		dei:EntityEmergingGrowthCompany
16	Entity Common Stock, Shares Outstanding	Concept (Shares)	As Of		dei:EntityCommonStockSharesOutstanding
17	1003 - Statement - Consolidated Statements of Financial Position	Network	*	*	http://www.stantec.com/taxonomy/role/StatementOfFinancialPositionCurrentNonCurrent-210000
18	Implied Table	Table	*	*	implied:Table
19	Statement of financial position [abstract]	Abstract			ifrs-full:StatementOfFinancialPositionAbstract
20	ASSETS	Abstract			ifrs-full:AssetsAbstract
21	Current	Abstract			ifrs-full:CurrentAssetsAbstract
22	Cash and cash equivalents	Concept (Monetary)	As Of	Debit	ifrs-full:CashAndCashEquivalents
23	Cash in escrow	Concept (Monetary)	As Of	Debit	ifrs-full:CurrentRestrictedCashAndCashEquivalents
24	Trade and other receivables	Concept (Monetary)	As Of	Debit	ifrs-full:TradeAndOtherCurrentReceivables
25	Unbilled receivables	Concept (Monetary)	As Of	Debit	stn:UnbilledReceivables
26	Contract assets	Concept (Monetary)	As Of	Debit	ifrs-full:CurrentContractAssets
27	Income taxes recoverable	Concept (Monetary)	As Of	Debit	ifrs-full:CurrentTaxAssetsCurrent
28	Prepaid expenses	Concept (Monetary)	As Of	Debit	ifrs-full:CurrentPrepaidExpenses
29	Other assets	Concept (Monetary)	As Of	Debit	ifrs-full:OtherCurrentAssets
30	Total current assets	Concept (Monetary)	As Of	Debit	ifrs-full:CurrentAssets
31	Non-current	Abstract			ifrs-full:NoncurrentAssetsAbstract
32	Property and equipment	Concept (Monetary)	As Of	Debit	ifrs-full:PropertyPlantAndEquipment
33	Goodwill	Concept (Monetary)	As Of	Debit	ifrs-full:Goodwill
34	Intangible assets	Concept (Monetary)	As Of	Debit	ifrs-full:IntangibleAssetsOtherThanGoodwill
35	Investments in joint ventures and associates	Concept (Monetary)	As Of	Debit	ifrs-full:InvestmentAccountedForUsingEquityMethod
36	Net employee defined benefit asset	Concept (Monetary)	As Of	Debit	ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan
37	Deferred tax assets	Concept (Monetary)	As Of	Debit	ifrs-full:DeferredTaxAssets
38	Other assets	Concept (Monetary)	As Of	Debit	ifrs-full:OtherNoncurrentAssets
39	Total assets	Concept (Monetary)	As Of	Debit	ifrs-full:Assets
40	LIABILITIES AND EQUITY	Abstract			ifrs-full:EquityAndLiabilitiesAbstract
41	Current	Abstract			ifrs-full:CurrentLiabilitiesAbstract
42	Trade and other payables	Concept (Monetary)	As Of	Credit	ifrs-full:TradeAndOtherCurrentPayables
43	Deferred revenue	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentContractLiabilities
44	Income taxes payable	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentTaxLiabilitiesCurrent
45	Long-term debt	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentPortionOfLongtermBorrowings
46	Provisions	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentProvisions
47	Other liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:OtherCurrentLiabilities
48	Total current liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentLiabilities
49	Non-current	Abstract			ifrs-full:NoncurrentLiabilitiesAbstract
50	Income taxes payable	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentTaxLiabilitiesNoncurrent
51	Long-term debt	Concept (Monetary)	As Of	Credit	ifrs-full:LongtermBorrowings
52	Provisions	Concept (Monetary)	As Of	Credit	ifrs-full:NoncurrentProvisions
53	Net employee defined benefit liability	Concept (Monetary)	As Of	Credit	ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan
54	Deferred tax liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:DeferredTaxLiabilities
55	Other liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:OtherNoncurrentLiabilities
56	Total liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:Liabilities
57	Shareholders' equity	Abstract			ifrs-full:EquityAbstract
58	Share capital	Concept (Monetary)	As Of	Credit	ifrs-full:IssuedCapital
59	Contributed surplus	Concept (Monetary)	As Of	Credit	ifrs-full:AdditionalPaidinCapital
60	Retained earnings	Concept (Monetary)	As Of	Credit	ifrs-full:RetainedEarnings
61	Accumulated other comprehensive income	Concept (Monetary)	As Of	Credit	ifrs-full:AccumulatedOtherComprehensiveIncome
62	Total shareholders' equity	Concept (Monetary)	As Of	Credit	ifrs-full:EquityAttributableToOwnersOfParent
63	Non-controlling interests	Concept (Monetary)	As Of	Credit	ifrs-full:NoncontrollingInterests
64	Total liabilities and equity	Concept (Monetary)	As Of	Credit	ifrs-full:EquityAndLiabilities
65	1004 - Statement - Consolidated Statements of Income	Network	*	*	http://www.stantec.com/taxonomy/role/StatementOfComprehensiveIncomeProfitOrLossByFunctionOfExpense-310000
66	Implied Table	Table	*	*	implied:Table
67	Profit or loss [abstract]	Abstract			ifrs-full:IncomeStatementAbstract
68	Continuing operations	Abstract			stn:ProfitLossFromContinuingOperationsAbstract
69	Gross revenue	Concept (Monetary)	For Period	Credit	stn:RevenueFromContinuingOperations
70	Less subconsultant and other direct expenses	Concept (Monetary)	For Period	Debit	stn:SubconsultantSubcontractorAndOtherDirectExpenses
71	Net revenue	Concept (Monetary)	For Period	Credit	stn:NetRevenue
72	Direct payroll costs	Concept (Monetary)	For Period	Debit	ifrs-full:CostOfSales
73	Gross margin	Concept (Monetary)	For Period	Credit	ifrs-full:GrossProfit
74	Administrative and marketing expenses	Concept (Monetary)	For Period	Debit	ifrs-full:SellingGeneralAndAdministrativeExpense
75	Depreciation of property and equipment	Concept (Monetary)	For Period	Debit	ifrs-full:DepreciationExpense
76	Amortization of intangible assets	Concept (Monetary)	For Period	Debit	ifrs-full:AmortisationExpense
77	Net interest expense	Concept (Monetary)	For Period	Credit	ifrs-full:InterestRevenueExpense
78	Other net finance expense	Concept (Monetary)	For Period	Credit	ifrs-full:FinanceIncomeCost
79	Share of income from joint ventures and associates	Concept (Monetary)	For Period	Credit	ifrs-full:ShareOfProfitLossOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
80	Foreign exchange loss (gain)	Concept (Monetary)	For Period	Credit	ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
81	Gain on disposition of a subsidiary	Concept (Monetary)	For Period	Credit	ifrs-full:GainsLossesOnDisposalsOfInvestments
82	Other expense (income)	Concept (Monetary)	For Period	Credit	ifrs-full:OtherOperatingIncomeExpense
83	Income before income taxes and discontinued operations	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLossBeforeTax
84	Income taxes	Abstract			ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
85	Current	Concept (Monetary)	For Period	Debit	ifrs-full:CurrentTaxExpenseIncome
86	Deferred	Concept (Monetary)	For Period	Debit	ifrs-full:DeferredTaxExpenseIncome
87	Total income taxes	Concept (Monetary)	For Period	Debit	ifrs-full:IncomeTaxExpenseContinuingOperations
88	Net income for the year from continuing operations	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLossFromContinuingOperations
89	Discontinued operations	Abstract			stn:ProfitLossFromDiscontinuingOperationsAbstract
90	Net loss from discontinued operations, net of tax	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLossFromDiscontinuedOperations
91	Net income for the year	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLoss
92	Earnings (Loss) per share, basic and diluted	Abstract			ifrs-full:BasicAndDilutedEarningsPerShareAbstract
93	Continuing operations	Concept (Share)	For Period		ifrs-full:BasicAndDilutedEarningsLossPerShareFromContinuingOperations
94	Discontinued operations	Concept (Share)	For Period		ifrs-full:BasicAndDilutedEarningsLossPerShareFromDiscontinuedOperations
95	Total basic and diluted earnings per share	Concept (Share)	For Period		ifrs-full:BasicAndDilutedEarningsLossPerShare
96	1005 - Statement - Consolidated Statements of Comprehensive Income (Loss)	Network	*	*	http://www.stantec.com/taxonomy/role/StatementOfComprehensiveIncomeOCIComponentsPresentedNetOfTax-410000
97	Implied Table	Table	*	*	implied:Table
98	Statement of comprehensive income [abstract]	Abstract			ifrs-full:StatementOfComprehensiveIncomeAbstract
99	Net income for the year	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLoss
100	Other comprehensive income (loss)	Abstract			ifrs-full:OtherComprehensiveIncomeAbstract
101	Items that may be reclassified to net income in subsequent periods:	Abstract			ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTaxAbstract
102	Exchange differences on translation of foreign operations	Concept (Monetary)	For Period	Credit	ifrs-full:OtherComprehensiveIncomeNetOfTaxExchangeDifferencesOnTranslation
103	Realized exchange difference on disposition of a subsidiary	Concept (Monetary)	For Period	Debit	ifrs-full:ReclassificationAdjustmentsOnExchangeDifferencesOnTranslationNetOfTax
104	Net unrealized loss on FVOCI financial assets	Concept (Monetary)	For Period	Credit	ifrs-full:GainsLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeBeforeTax
105	Net realized gain on FVOCI financial assets transferred to income	Concept (Monetary)	For Period	Debit	ifrs-full:ReclassificationAdjustmentsOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeBeforeTax
106	Total items that may be reclassified to net income in subsequent periods	Concept (Monetary)	For Period	Credit	ifrs-full:OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTax
107	Items not to be reclassified to net income:	Abstract			ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTaxAbstract
108	Remeasurement (loss) gain on net employee defined benefit liability net of deferred tax recovery of $2.0 (2017 - tax expense of $2.4)	Concept (Monetary)	For Period	Credit	ifrs-full:OtherComprehensiveIncomeNetOfTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
109	Other comprehensive income (loss) for the year, net of tax	Concept (Monetary)	For Period	Credit	ifrs-full:OtherComprehensiveIncome
110	Total comprehensive income (loss) for the year, net of tax	Concept (Monetary)	For Period	Credit	ifrs-full:ComprehensiveIncome
111	1006 - Statement - Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)	Network	*	*	http://www.stantec.com/taxonomy/role/StatementOfComprehensiveIncomeOCIComponentsPresentedNetOfTax-410000Parenthetical
112	Implied Table	Table	*	*	implied:Table
113	Statement of comprehensive income [abstract]	Abstract			ifrs-full:StatementOfComprehensiveIncomeAbstract
114	Deferred tax related to remeasurement gains (losses) on net employee defined benefit liability	Concept (Monetary)	For Period	Debit	ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome
115	1007 - Statement - Consolidated Statements of Shareholders' Equity	Network	*	*	http://www.stantec.com/taxonomy/role/StatementOfChangesInEquity-610000
116	Statement of changes in equity [table]	Table	*	*	ifrs-full:StatementOfChangesInEquityTable
117	Components of equity [axis]	Axis			ifrs-full:ComponentsOfEquityAxis
118	Equity Securities [Member]	Member			ifrs-full:EquityMember
119	Share capital [member]	Member			ifrs-full:IssuedCapitalMember
120	Contributed surplus [member]	Member			ifrs-full:AdditionalPaidinCapitalMember
121	Retained earnings [member]	Member			ifrs-full:RetainedEarningsMember
122	Accumulated other comprehensive income (loss) [member]	Member			ifrs-full:AccumulatedOtherComprehensiveIncomeMember
123	Retrospective application and retrospective restatement [axis]	Axis			ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
124	Restated [member]	Member			ifrs-full:RestatedMember
125	Previously stated [member]	Member			ifrs-full:PreviouslyStatedMember
126	Increase (decrease) due to application of IFRS 15 [member]	Member			ifrs-full:FinancialEffectOfChangesInAccountingPolicyMember
127	Adjusted balance [member]	Member			stn:RestatedBalanceMember
128	Statement of changes in equity [line items]	LineItems			ifrs-full:StatementOfChangesInEquityLineItems
129	Beginning balance	Concept (Monetary)	As Of	Credit	ifrs-full:EquityAttributableToOwnersOfParent
130	Beginning balance, shares	Concept (Shares)	As Of		ifrs-full:NumberOfSharesOutstanding
131	Net income	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLoss
132	Other comprehensive income	Concept (Monetary)	For Period	Credit	ifrs-full:OtherComprehensiveIncome
133	Total comprehensive income	Concept (Monetary)	For Period	Credit	ifrs-full:ComprehensiveIncome
134	Share options exercised for cash	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughExerciseOfOptions
135	Share options exercised for cash, shares	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
136	Share-based compensation expense	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughSharebasedPaymentTransactions
137	Shares repurchased under Normal Course Issuer Bid	Concept (Monetary)	For Period	Debit	ifrs-full:PurchaseOfTreasuryShares
138	Shares repurchased under Normal Course Issuer Bid, shares	Concept (Shares)	For Period		stn:IncreaseDecreaseInNumberOfSharesRepurchased
139	Reclassification of fair value of share options previously expensed	Concept (Monetary)	For Period	Credit	stn:ReclassificationOfFairValueOfShareOptionsPreviouslyExpensedEquity
140	Dividends declared	Concept (Monetary)	For Period	Debit	ifrs-full:DividendsPaid
141	Ending balance	Concept (Monetary)	As Of	Credit	ifrs-full:EquityAttributableToOwnersOfParent
142	Ending balance, shares	Concept (Shares)	As Of		ifrs-full:NumberOfSharesOutstanding
143	1008 - Statement - Consolidated Statements of Cash Flows	Network	*	*	http://www.stantec.com/taxonomy/role/StatementOfCashFlowsDirectMethod-510000
144	Implied Table	Table	*	*	implied:Table
145	Statement of cash flows [abstract]	Abstract			ifrs-full:StatementOfCashFlowsAbstract
146	CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES	Abstract			ifrs-full:CashFlowsFromUsedInOperatingActivitiesAbstract
147	Cash receipts from clients	Concept (Monetary)	For Period	Debit	ifrs-full:ReceiptsFromSalesOfGoodsAndRenderingOfServices
148	Cash paid to suppliers	Concept (Monetary)	For Period	Credit	ifrs-full:PaymentsToSuppliersForGoodsAndServices
149	Cash paid to employees	Concept (Monetary)	For Period	Credit	ifrs-full:PaymentsToAndOnBehalfOfEmployees
150	Interest received	Concept (Monetary)	For Period	Debit	ifrs-full:InterestReceivedClassifiedAsOperatingActivities
151	Interest paid	Concept (Monetary)	For Period	Credit	ifrs-full:InterestPaidClassifiedAsOperatingActivities
152	Finance costs paid	Concept (Monetary)	For Period	Credit	ifrs-full:FinanceCostsPaidClassifiedAsOperatingActivities
153	Income taxes paid	Concept (Monetary)	For Period	Credit	ifrs-full:IncomeTaxesPaidClassifiedAsOperatingActivities
154	Income taxes recovered	Concept (Monetary)	For Period	Debit	ifrs-full:IncomeTaxesRefundClassifiedAsOperatingActivities
155	Cash flows from operating activities from continuing operations	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInOperatingActivitiesContinuingOperations
156	Cash flows (used in) from operating activities from discontinued operations	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInOperatingActivitiesDiscontinuedOperations
157	Net cash flows from operating activities	Concept (Monetary)	For Period		ifrs-full:CashFlowsFromUsedInOperatingActivities
158	CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES	Abstract			ifrs-full:CashFlowsFromUsedInInvestingActivitiesAbstract
159	Business acquisitions, net of cash acquired	Concept (Monetary)	For Period	Credit	ifrs-full:CashFlowsUsedInObtainingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
160	Proceeds from lease inducements	Concept (Monetary)	For Period	Debit	stn:ProceedsFromLeaseInducementsClassifiedAsInvestingActivities
161	Proceeds on disposition of a subsidiary	Concept (Monetary)	For Period	Debit	stn:CashInflowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
162	Cash sold on disposition of subsidiary	Concept (Monetary)	For Period	Credit	stn:CashOutFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
163	Income taxes paid on disposition of subsidiary	Concept (Monetary)	For Period	Credit	ifrs-full:IncomeTaxesPaidRefundClassifiedAsInvestingActivities
164	Purchase of intangible assets	Concept (Monetary)	For Period	Credit	ifrs-full:PurchaseOfIntangibleAssetsClassifiedAsInvestingActivities
165	Purchase of property and equipment	Concept (Monetary)	For Period	Credit	ifrs-full:PurchaseOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities
166	Proceeds (purchase) from other investing activities	Concept (Monetary)	For Period	Debit	ifrs-full:OtherInflowsOutflowsOfCashClassifiedAsInvestingActivities
167	Cash flows (used in) from investing activities from continuing operations	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInInvestingActivitiesContinuingOperations
168	Cash flows (used in) investing activities from discontinued operations, net of taxes paid	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInInvestingActivitiesDiscontinuedOperations
169	Net cash flows (used in) from investing activities	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInInvestingActivities
170	CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES	Abstract			ifrs-full:CashFlowsFromUsedInFinancingActivitiesAbstract
171	Net proceeds (repayment) from revolving credit facility	Concept (Monetary)	For Period	Credit	stn:ProceedsFromOrRepaymentsOfBorrowingsClassifiedAsFinancingActivities
172	Repayment of term loan	Concept (Monetary)	For Period	Credit	ifrs-full:RepaymentsOfCurrentBorrowings
173	Repayment of other long-term debt	Concept (Monetary)	For Period	Credit	ifrs-full:RepaymentsOfNoncurrentBorrowings
174	Payment of finance lease obligations	Concept (Monetary)	For Period	Credit	ifrs-full:PaymentsOfFinanceLeaseLiabilitiesClassifiedAsFinancingActivities
175	Repurchase of shares for cancellation	Concept (Monetary)	For Period	Credit	ifrs-full:PaymentsToAcquireOrRedeemEntitysShares
176	Proceeds from issue of share capital	Concept (Monetary)	For Period	Debit	ifrs-full:ProceedsFromIssueOfOrdinaryShares
177	Payment of dividends to shareholders	Concept (Monetary)	For Period	Credit	ifrs-full:DividendsPaidClassifiedAsFinancingActivities
178	Cash flows from (used in) financing activities from continuing operations	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInFinancingActivitiesContinuingOperations
179	Cash flows (used in) financing activities from discontinued operations	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInFinancingActivitiesDiscontinuedOperations
180	Net cash flows from (used in) financing activities	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromUsedInFinancingActivities
181	Foreign exchange gain (loss) on cash held in foreign currency	Concept (Monetary)	For Period	Debit	ifrs-full:EffectOfExchangeRateChangesOnCashAndCashEquivalents
182	Net (decrease) increase in cash and cash equivalents	Concept (Monetary)	For Period	Debit	ifrs-full:IncreaseDecreaseInCashAndCashEquivalents
183	Cash and cash equivalents, beginning of the year	Concept (Monetary)	As Of	Debit	ifrs-full:CashAndCashEquivalents
184	Cash and cash equivalents, end of the year	Concept (Monetary)	As Of	Debit	ifrs-full:CashAndCashEquivalents
185	1009 - Disclosure - Corporate Information	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfGeneralInformationAboutFinancialStatementsExplanatory
186	Implied Table	Table	*	*	implied:Table
187	Text block [abstract]	Abstract			stn:TextBlockAbstract
188	Corporate Information	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfGeneralInformationAboutFinancialStatementsExplanatory
189	1010 - Disclosure - Basis of Preparation	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfBasisOfPreparationOfFinancialStatementsExplanatory
190	Implied Table	Table	*	*	implied:Table
191	Text block [abstract]	Abstract			stn:TextBlockAbstract
192	Basis of Preparation	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfBasisOfPreparationOfFinancialStatementsExplanatory
193	1011 - Disclosure - Basis of Consolidation	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfBasisOfConsolidationExplanatory
194	Implied Table	Table	*	*	implied:Table
195	Text block [abstract]	Abstract			stn:TextBlockAbstract
196	Basis of Consolidation	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfBasisOfConsolidationExplanatory
197	1012 - Disclosure - Summary of Significant Accounting Policies	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
198	Implied Table	Table	*	*	implied:Table
199	Text block [abstract]	Abstract			stn:TextBlockAbstract
200	Summary of Significant Accounting Policies	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
201	1013 - Disclosure - Significant Accounting Judgments, Estimates, and Assumptions	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfAccountingJudgementsAndEstimatesExplanatory
202	Implied Table	Table	*	*	implied:Table
203	Text block [abstract]	Abstract			stn:TextBlockAbstract
204	Significant Accounting Judgments, Estimates, and Assumptions	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfAccountingJudgementsAndEstimatesExplanatory
205	1014 - Disclosure - Recent Accounting Pronouncements and Changes to Accounting Policies	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfChangesInAccountingPoliciesExplanatory
206	Implied Table	Table	*	*	implied:Table
207	Text block [abstract]	Abstract			stn:TextBlockAbstract
208	Recent Accounting Pronouncements and Changes to Accounting Policies	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfChangesInAccountingPoliciesExplanatory
209	1015 - Disclosure - Business Acquisitions	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfBusinessCombinationsExplanatory
210	Implied Table	Table	*	*	implied:Table
211	Text block [abstract]	Abstract			stn:TextBlockAbstract
212	Business Acquisitions	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfBusinessCombinationsExplanatory
213	1016 - Disclosure - Discontinued Operations and Disposition of Subsidiaries	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfDiscontinuedOperationsExplanatory
214	Implied Table	Table	*	*	implied:Table
215	Text block [abstract]	Abstract			stn:TextBlockAbstract
216	Discontinued Operations and Disposition of Subsidiaries	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfDiscontinuedOperationsExplanatory
217	1017 - Disclosure - Cash and Cash Equivalents	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCashAndCashEquivalentsExplanatory
218	Implied Table	Table	*	*	implied:Table
219	Text block [abstract]	Abstract			stn:TextBlockAbstract
220	Cash and Cash Equivalents	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfCashAndCashEquivalentsExplanatory
221	1018 - Disclosure - Trade and Other Receivables	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfTradeAndOtherReceivablesExplanatory
222	Implied Table	Table	*	*	implied:Table
223	Text block [abstract]	Abstract			stn:TextBlockAbstract
224	Trade and Other Receivables	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfTradeAndOtherReceivablesExplanatory
225	1019 - Disclosure - Property and Equipment	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfPropertyPlantAndEquipmentExplanatory
226	Implied Table	Table	*	*	implied:Table
227	Text block [abstract]	Abstract			stn:TextBlockAbstract
228	Property and Equipment	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfPropertyPlantAndEquipmentExplanatory
229	1020 - Disclosure - Goodwill	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfGoodwillExplanatory
230	Implied Table	Table	*	*	implied:Table
231	Text block [abstract]	Abstract			stn:TextBlockAbstract
232	Goodwill	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfGoodwillExplanatory
233	1021 - Disclosure - Intangible Assets	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfIntangibleAssetsExplanatory
234	Implied Table	Table	*	*	implied:Table
235	Text block [abstract]	Abstract			stn:TextBlockAbstract
236	Intangible Assets	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfIntangibleAssetsExplanatory
237	1022 - Disclosure - Other Assets	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherAssetsExplanatory
238	Implied Table	Table	*	*	implied:Table
239	Text block [abstract]	Abstract			stn:TextBlockAbstract
240	Other Assets	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfOtherAssetsExplanatory
241	1023 - Disclosure - Trade and Other Payables	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfTradeAndOtherPayablesExplanatory
242	Implied Table	Table	*	*	implied:Table
243	Text block [abstract]	Abstract			stn:TextBlockAbstract
244	Trade and Other Payables	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfTradeAndOtherPayablesExplanatory
245	1024 - Disclosure - Long-Term Debt	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfBorrowingsExplanatory
246	Implied Table	Table	*	*	implied:Table
247	Text block [abstract]	Abstract			stn:TextBlockAbstract
248	Long-Term Debt	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfBorrowingsExplanatory
249	1025 - Disclosure - Provisions	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherProvisionsContingentLiabilitiesAndContingentAssetsExplanatory
250	Implied Table	Table	*	*	implied:Table
251	Text block [abstract]	Abstract			stn:TextBlockAbstract
252	Provisions	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfOtherProvisionsContingentLiabilitiesAndContingentAssetsExplanatory
253	1026 - Disclosure - Employee Defined Benefit Obligations	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfEmployeeBenefitsExplanatory
254	Implied Table	Table	*	*	implied:Table
255	Text block [abstract]	Abstract			stn:TextBlockAbstract
256	Employee Defined Benefit Obligations	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfEmployeeBenefitsExplanatory
257	1027 - Disclosure - Other Liabilities	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherLiabilitiesExplanatory
258	Implied Table	Table	*	*	implied:Table
259	Text block [abstract]	Abstract			stn:TextBlockAbstract
260	Other Liabilities	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfOtherLiabilitiesExplanatory
261	1028 - Disclosure - Commitments	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCommitmentsExplanatory
262	Implied Table	Table	*	*	implied:Table
263	Text block [abstract]	Abstract			stn:TextBlockAbstract
264	Commitments	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfCommitmentsExplanatory
265	1029 - Disclosure - Contingencies and Guarantees	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfContingenciesAndGuaranteesExplanatory
266	Implied Table	Table	*	*	implied:Table
267	Text block [abstract]	Abstract			stn:TextBlockAbstract
268	Contingencies and Guarantees	Concept (Text Block (HTML))	For Period		stn:DisclosureOfContingenciesAndGuaranteesExplanatory
269	1030 - Disclosure - Share Capital	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfShareCapitalReservesAndOtherEquityInterestExplanatory
270	Implied Table	Table	*	*	implied:Table
271	Text block [abstract]	Abstract			stn:TextBlockAbstract
272	Share Capital	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfShareCapitalReservesAndOtherEquityInterestExplanatory
273	1031 - Disclosure - Fair Value Measurements	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfFairValueMeasurementExplanatory
274	Implied Table	Table	*	*	implied:Table
275	Text block [abstract]	Abstract			stn:TextBlockAbstract
276	Fair Value Measurements	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfFairValueMeasurementExplanatory
277	1032 - Disclosure - Financial Instruments	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinancialInstrumentsExplanatory
278	Implied Table	Table	*	*	implied:Table
279	Text block [abstract]	Abstract			stn:TextBlockAbstract
280	Financial Instruments	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfFinancialInstrumentsExplanatory
281	1033 - Disclosure - Capital Management	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCapitalManagementExplanatory
282	Implied Table	Table	*	*	implied:Table
283	Text block [abstract]	Abstract			stn:TextBlockAbstract
284	Capital Management	Concept (Text Block (HTML))	For Period		stn:DisclosureOfCapitalManagementExplanatory
285	1034 - Disclosure - Income Taxes	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfIncomeTaxExplanatory
286	Implied Table	Table	*	*	implied:Table
287	Text block [abstract]	Abstract			stn:TextBlockAbstract
288	Income Taxes	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfIncomeTaxExplanatory
289	1035 - Disclosure - Net Interest Expense and Other Net Finance Expense	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfFinanceCostExplanatory
290	Implied Table	Table	*	*	implied:Table
291	Text block [abstract]	Abstract			stn:TextBlockAbstract
292	Net Interest Expense and Other Net Finance Expense	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfFinanceCostExplanatory
293	1036 - Disclosure - Revenue	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfRevenueExplanatory
294	Implied Table	Table	*	*	implied:Table
295	Text block [abstract]	Abstract			stn:TextBlockAbstract
296	Revenue	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfRevenueExplanatory
297	1037 - Disclosure - Employee Costs from Continuing Operations	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfEmployeeCostsExplanatory
298	Implied Table	Table	*	*	implied:Table
299	Text block [abstract]	Abstract			stn:TextBlockAbstract
300	Employee Costs from Continuing Operations	Concept (Text Block (HTML))	For Period		stn:DisclosureOfEmployeeCostsExplanatory
301	1038 - Disclosure - Other Expense (Income)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherExpenseIncomeExplanatory
302	Implied Table	Table	*	*	implied:Table
303	Text block [abstract]	Abstract			stn:TextBlockAbstract
304	Other Expense (Income)	Concept (Text Block (HTML))	For Period		stn:DisclosureOfOtherExpenseIncomeExplanatory
305	1039 - Disclosure - Weighted Average Shares Outstanding	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfWeightedAverageNumberOfSharesExplanatory
306	Implied Table	Table	*	*	implied:Table
307	Investments accounted for using equity method [abstract]	Abstract			ifrs-full:InvestmentsAccountedForUsingEquityMethodAbstract
308	Weighted Average Shares Outstanding	Concept (Text Block (HTML))	For Period		stn:DisclosureOfWeightedAverageNumberOfSharesExplanatory
309	1040 - Disclosure - Cash Flow Information	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCashFlowStatementExplanatory
310	Implied Table	Table	*	*	implied:Table
311	Text block [abstract]	Abstract			stn:TextBlockAbstract
312	Cash Flow Information	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfCashFlowStatementExplanatory
313	1041 - Disclosure - Related-Party Disclosures	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfRelatedPartyExplanatory
314	Implied Table	Table	*	*	implied:Table
315	Text block [abstract]	Abstract			stn:TextBlockAbstract
316	Related-Party Disclosures	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfRelatedPartyExplanatory
317	1042 - Disclosure - Segmented Information	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfEntitysReportableSegmentsExplanatory
318	Implied Table	Table	*	*	implied:Table
319	Text block [abstract]	Abstract			stn:TextBlockAbstract
320	Segmented Information	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfEntitysReportableSegmentsExplanatory
321	1043 - Disclosure - Investment Tax Credits	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfInvestmentTaxCreditsExplanatoy
322	Implied Table	Table	*	*	implied:Table
323	Text block [abstract]	Abstract			stn:TextBlockAbstract
324	Investment Tax Credits	Concept (Text Block (HTML))	For Period		stn:DisclosureOfInvestmentTaxCreditsExplanatoy
325	1044 - Disclosure - Events after the Reporting Period	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfEventsAfterReportingPeriodExplanatory
326	Implied Table	Table	*	*	implied:Table
327	Text block [abstract]	Abstract			stn:TextBlockAbstract
328	Events after the Reporting Period	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfEventsAfterReportingPeriodExplanatory
329	1045 - Disclosure - Comparative Figures	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfReclassificationsOrChangesInPresentationExplanatory
330	Implied Table	Table	*	*	implied:Table
331	Text block [abstract]	Abstract			stn:TextBlockAbstract
332	Comparative Figures	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfReclassificationsOrChangesInPresentationExplanatory
333	1046 - Disclosure - Summary of Significant Accounting Policies (Policies)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfSummaryOfSignificantAccountingPoliciesExplanatoryPolicies
334	Implied Table	Table	*	*	implied:Table
335	Text block [abstract]	Abstract			stn:TextBlockAbstract
336	Cash and cash equivalents	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyToDetermineComponentsOfCashAndCashEquivalents
337	Property and equipment	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForPropertyPlantAndEquipmentExplanatory
338	Intangible assets	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForIntangibleAssetsOtherThanGoodwillExplanatory
339	Leases	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForLeasesExplanatory
340	Investments in joint arrangements and associates	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForInvestmentInAssociatesAndJointVenturesExplanatory
341	Provisions	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForProvisionsExplanatory
342	Foreign currency translation	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForForeignCurrencyTranslationExplanatory
343	Financial instruments	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForFinancialInstrumentsExplanatory
344	Impairment	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForImpairmentOfAssetsExplanatory
345	Revenue recognition	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForRecognitionOfRevenue
346	Employee benefit plans	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForEmployeeBenefitsExplanatory
347	Taxes	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForIncomeTaxExplanatory
348	Share-based payment transactions	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForSharebasedPaymentTransactionsExplanatory
349	Earnings per share	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForEarningsPerShareExplanatory
350	Business combinations and goodwill	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForBusinessCombinationsAndGoodwillExplanatory
351	Dividends	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForDividendsExplanatory
352	Non-current assets held for sale and discontinued operations	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForNoncurrentAssetsOrDisposalGroupsClassifiedAsHeldForSaleAndDiscontinuedOperationsExplanatory
353	Provision for self-insured liabilities	Concept (Text Block (HTML))	For Period		stn:DescriptionOfAccountingPolicyForProvisionForSelfInsuredLiabilities
354	Business combinations	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForBusinessCombinationsExplanatory
355	Impairment of goodwill	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForImpairmentOfNonfinancialAssetsExplanatory
356	Fair value of financial instruments	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForFinancialInstrumentsAtFairValueThroughProfitOrLossExplanatory
357	1047 - Disclosure - Summary of Significant Accounting Policies (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfSummaryOfSignificantAccountingPoliciesExplanatoryTables
358	Implied Table	Table	*	*	implied:Table
359	Text block [abstract]	Abstract			stn:TextBlockAbstract
360	Schedule of Estimated Useful Lives and Depreciation Calculation Methods	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfAccountingPolicyForDepreciationExpenseExplanatory
361	1048 - Disclosure - Recent Accounting Pronouncements and Changes to Accounting Policies (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfChangesInAccountingPoliciesExplanatoryTables
362	Statement [table]	Table	*	*	stn:StatementTable
363	Retrospective application and retrospective restatement [axis]	Axis			ifrs-full:RetrospectiveApplicationAndRetrospectiveRestatementAxis
364	Restated [member]	Member			ifrs-full:RestatedMember
365	Increase (decrease) due to application of IFRS 15 [member]	Member			ifrs-full:IncreaseDecreaseDueToApplicationOfIFRS15Member
366	Increase (decrease) due to application of IFRS 9 [member]	Member			stn:IncreaseDecreaseDueToApplicationOfIFRS9Member
367	Statement [LineItems]	LineItems			stn:StatementLineItems
368	Summary of Impact of Changes to Accounting Policies on After-tax	Concept (Text Block (HTML))	For Period		ifrs-full:DescriptionOfExpectedImpactOfInitialApplicationOfNewStandardsOrInterpretations
369	Summary of Impacts of Adopting IFRS 15 in Consolidated Statement of Financial Position	Concept (Text Block (HTML))	For Period		stn:DisclosureOfExpectedImpactOfInitialApplicationOfIFRS15OnStatementOfFinancialPositionExplanatory
370	Summary of Impacts of Adopting IFRS 15 in Consolidated Statements of Income and Comprehensive Income (Loss)	Concept (Text Block (HTML))	For Period		stn:DisclosureOfExpectedImpactOfInitialApplicationOfIFRS15OnIncomeStatementItemsExplanatory
371	Summary of Measurement Category of Financial Assets	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfFinancialAssetsAtDateOfInitialApplicationOfIFRS9Explanatory
372	1049 - Disclosure - Business Acquisitions (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfBusinessCombinationsExplanatoryTables
373	Implied Table	Table	*	*	implied:Table
374	Text block [abstract]	Abstract			stn:TextBlockAbstract
375	Summary of Consideration for Assets Acquired and Liabilities Assumed	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfDetailedInformationAboutBusinessCombinationsExplanatory
376	Summary of Consideration of Business Combinations	Concept (Text Block (HTML))	For Period		stn:DisclosureOfDetailedInformationAboutBusinessCombinationsCashConsiderationExplanatory
377	Summary of Notes Payable in Business Combination	Concept (Text Block (HTML))	For Period		stn:DisclosureOfNotesPayableInBusinessCombinationExplanatory
378	1050 - Disclosure - Discontinued Operations and Disposition of Subsidiaries (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfDiscontinuedOperationsExplanatoryTables
379	Statement [table]	Table	*	*	stn:StatementTable
380	Continuing and discontinued operations [axis]	Axis			ifrs-full:ContinuingAndDiscontinuedOperationsAxis
381	Continuing operations [Member]	Member			ifrs-full:ContinuingOperationsMember
382	Disposal of major subsidiary [member]	Member			ifrs-full:DisposalOfMajorSubsidiaryMember
383	Statement [LineItems]	LineItems			stn:StatementLineItems
384	Summary of Net Loss from Discontinued Operations	Concept (Text Block (HTML))	For Period		stn:DisclosureOfNetIncomeFromDiscontinuedOperationsExplanatory
385	Summary of Disposition of Subsidiary and Construction Services	Concept (Text Block (HTML))	For Period		stn:DisclosureOfDetailedInformationAboutDisposalOfSubsidiariesExplanatory
386	1051 - Disclosure - Cash and Cash Equivalents (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCashAndCashEquivalentsExplanatoryTables
387	Implied Table	Table	*	*	implied:Table
388	Text block [abstract]	Abstract			stn:TextBlockAbstract
389	Summary of Cash and Cash Equivalents	Concept (Text Block (HTML))	For Period		stn:DisclosureOfDetailedInformationAboutCashAndCashEquivalentsExplanatory
390	1052 - Disclosure - Trade and Other Receivables (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfTradeAndOtherReceivablesExplanatoryTables
391	Implied Table	Table	*	*	implied:Table
392	Text block [abstract]	Abstract			stn:TextBlockAbstract
393	Schedule of Trade and Other Receivables	Concept (Text Block (HTML))	For Period		stn:DisclosureOfTradeHoldBacksAndOtherReceivablesExplanatory
394	Schedule of Gross Trade Receivables Aging Analysis	Concept (Text Block (HTML))	For Period		stn:DisclosureOfGrossTradeReceivablesAgingAnalysisExplanatory
395	1053 - Disclosure - Property and Equipment (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfPropertyPlantAndEquipmentExplanatoryTables
396	Implied Table	Table	*	*	implied:Table
397	Text block [abstract]	Abstract			stn:TextBlockAbstract
398	Schedule of Property and Equipment	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfDetailedInformationAboutPropertyPlantAndEquipmentExplanatory
399	1054 - Disclosure - Goodwill (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfGoodwillExplanatoryTables
400	Implied Table	Table	*	*	implied:Table
401	Text block [abstract]	Abstract			stn:TextBlockAbstract
402	Schedule of Reconciliation of Changes in Goodwill	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillExplanatory
403	Schedule of Goodwill Allocated	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesExplanatory
404	Summary of Most Sensitive Key Assumptions Used for CGUs	Concept (Text Block (HTML))	For Period		stn:DisclosureOfKeyAssumptionsUsedForImpairmentTestsOfIndividualAssetOrCashGeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesExplanatory
405	1055 - Disclosure - Intangible Assets (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfIntangibleAssetsExplanatoryTables
406	Implied Table	Table	*	*	implied:Table
407	Text block [abstract]	Abstract			stn:TextBlockAbstract
408	Summary of Intangible Assets	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfDetailedInformationAboutIntangibleAssetsExplanatory
409	1056 - Disclosure - Other Assets (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherAssetsExplanatoryTables
410	Implied Table	Table	*	*	implied:Table
411	Text block [abstract]	Abstract			stn:TextBlockAbstract
412	Schedule of Other Assets	Concept (Text Block (HTML))	For Period		stn:DisclosureOfOtherAssetsNoncurrentAssetsExplanatory
413	Disclosure of Fair Value and Amortized Cost	Concept (Text Block (HTML))	For Period		stn:DisclosureofinvestmentsheldforselfinsuredliabilitiesatfairvalueandamortizedcostExplanatory
414	Disclosure of the Bond Portfolio Stated at Fair Value	Concept (Text Block (HTML))	For Period		stn:DisclosureOfInvestmentsHeldForSelfInsuredLiabilitiesMaturityOfBondPortfolioAtFairValueExplanatory
415	1057 - Disclosure - Trade and Other Payables (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfTradeAndOtherPayablesExplanatoryTables
416	Implied Table	Table	*	*	implied:Table
417	Text block [abstract]	Abstract			stn:TextBlockAbstract
418	Summary of Trade and Other Payables	Concept (Text Block (HTML))	For Period		stn:DisclosureOfDetailedInformationAboutTradeAndOtherPayablesExplanatory
419	1058 - Disclosure - Long-Term Debt (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfBorrowingsExplanatoryTables
420	Implied Table	Table	*	*	implied:Table
421	Text block [abstract]	Abstract			stn:TextBlockAbstract
422	Summary of Long Term Debt	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsExplanatory
423	Future Minimum Lease Payments and Present Value of the Net Minimum Lease Payments under Finance Leases	Concept (Text Block (HTML))	For Period		stn:DisclosureOfFinanceLeasesByLesseeExplanatory
424	1059 - Disclosure - Provisions (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherProvisionsContingentLiabilitiesAndContingentAssetsExplanatoryTables
425	Implied Table	Table	*	*	implied:Table
426	Text block [abstract]	Abstract			stn:TextBlockAbstract
427	Summary of Provisions	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfOtherProvisionsExplanatory
428	1060 - Disclosure - Employee Defined Benefit Obligations (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfEmployeeBenefitsExplanatoryTables
429	Implied Table	Table	*	*	implied:Table
430	Text block [abstract]	Abstract			stn:TextBlockAbstract
431	Summary of Employee Defined Benefit Obligations	Concept (Text Block (HTML))	For Period		stn:DisclosureOfDefinedBenefitObligationsExplanatory
432	Summary of Reconciliation for Net Defined Benefit Liability	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetExplanatory
433	Summary of Net Defined Benefit Asset	Concept (Text Block (HTML))	For Period		stn:DisclosureOfNetDefinedBenefitExpenseExplanatory
434	Summary of Major Categories of Plan Assets, Measured at Fair Value	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfFairValueOfPlanAssetsExplanatory
435	Summary of Principal Assumptions Used In Determining Pension Benefit Obligations	Concept (Text Block (HTML))	For Period		stn:DisclosureOfActuarialAssumptionsExplanatory
436	Summary of Quantitative Sensitivity Analyses Impact on Defined Benefit Obligation for Significant Assumptions	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsExplanatory
437	1061 - Disclosure - Other Liabilities (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfOtherLiabilitiesExplanatoryTables
438	Implied Table	Table	*	*	implied:Table
439	Text block [abstract]	Abstract			stn:TextBlockAbstract
440	Summary of Other Liabilities	Concept (Text Block (HTML))	For Period		stn:DisclosureOfDetailedInformationAboutOtherLiabilitiesExplanatory
441	1062 - Disclosure - Commitments (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCommitmentsExplanatoryTables
442	Implied Table	Table	*	*	implied:Table
443	Text block [abstract]	Abstract			stn:TextBlockAbstract
444	Summary of Future Minimum Lease Payments Payable Under Noncancellable Operating Leases	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeExplanatory
445	1063 - Disclosure - Share Capital (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfShareCapitalReservesAndOtherEquityInterestExplanatoryTables
446	Implied Table	Table	*	*	implied:Table
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448	Summary of Dividends Declared and Recorded in the Consolidated Financial Statements	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfDividendsExplanatory
449	Summary of Granted Share Options	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfNumberAndWeightedAverageExercisePricesOfShareOptionsExplanatory
450	Summary of Outstanding Share Options	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsExplanatory
451	Summary of Weighted Average Assumptions	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfIndirectMeasurementOfFairValueOfGoodsOrServicesReceivedShareOptionsGrantedDuringPeriodExplanatory
452	Summary of Non-Vested Options	Concept (Text Block (HTML))	For Period		ifrs-full:DisclosureOfAdditionalInformationAboutDefinedBenefitPlansExplanatory
453	1064 - Disclosure - Fair Value Measurements (Tables)	Network	*	*	http://www.stantec.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfFairValueMeasurementExplanatoryTables
454	Statement [table]	Table	*	*	stn:StatementTable
455	Measurement [axis]	Axis			ifrs-full:MeasurementAxis
456	Aggregated measurement [member]	Member			ifrs-full:AggregatedMeasurementMember
457	Recurring fair value measurement [member]	Member			ifrs-full:RecurringFairValueMeasurementMember
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676	Assets and liabilities acquired	Abstract			ifrs-full:AmountsRecognisedAsOfAcquisitionDateForEachMajorClassOfAssetsAcquiredAndLiabilitiesAssumedAbstract
677	Cash acquired	Concept (Monetary)	As Of	Debit	ifrs-full:CashAndCashEquivalentsRecognisedAsOfAcquisitionDate
678	Trade receivables	Concept (Monetary)	As Of	Debit	stn:NonCashWorkingCapitalRelatedToTradeReceivablesRecognisedAsOfAcquisitionDate
679	Unbilled receivables	Concept (Monetary)	As Of	Debit	stn:NonCashWorkingCapitalRelatedToUnbilledReceivablesRecognisedAsOfAcquisitionDate
680	Accounts payable	Concept (Monetary)	As Of	Credit	stn:NonCashWorkingCapitalRelatedToAccountsPayableAsOfAcquisitionDate
681	Other non-cash working capital	Concept (Monetary)	As Of	Credit	stn:NonCashWorkingCapitalRelatedToOtherNonCashWorkingCapitalPayableAsOfAcquisitionDate
682	Property and equipment	Concept (Monetary)	As Of	Debit	ifrs-full:PropertyPlantAndEquipmentRecognisedAsOfAcquisitionDate
683	Intangible assets	Concept (Monetary)	As Of	Debit	ifrs-full:IdentifiableIntangibleAssetsRecognisedAsOfAcquisitionDate
684	Deferred tax assets	Concept (Monetary)	As Of	Debit	ifrs-full:DeferredTaxAssetsRecognisedAsOfAcquisitionDate
685	Net employee defined benefit liability	Concept (Monetary)	As Of	Credit	stn:RetirementBenefitObligationsRecognisedAsOfAcquisitionDate
686	Provisions	Concept (Monetary)	As Of	Credit	stn:ProvisionsRecognisedAsOfAcquisitionDate
687	Deferred tax liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:DeferredTaxLiabilitiesRecognisedAsOfAcquisitionDate
688	Total identifiable net assets at fair value	Concept (Monetary)	As Of	Debit	ifrs-full:IdentifiableAssetsAcquiredLiabilitiesAssumed
689	Goodwill arising on acquisitions	Concept (Monetary)	As Of	Debit	ifrs-full:GoodwillRecognisedAsOfAcquisitionDate
690	Consideration	Concept (Monetary)	As Of	Credit	ifrs-full:AcquisitiondateFairValueOfTotalConsiderationTransferred
691	1085 - Disclosure - Business Acquisitions - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureBusinessAcquisitionsAdditionalInformation
692	Disclosure of detailed information about business combination [table]	Table	*	*	ifrs-full:DisclosureOfBusinessCombinationsTable
693	Business combinations [axis]	Axis			ifrs-full:BusinessCombinationsAxis
694	Entity's total for business combinations [member]	Member			ifrs-full:EntitysTotalForBusinessCombinationsMember
695	Aggregated individually immaterial business combinations [member]	Member			ifrs-full:AggregatedIndividuallyImmaterialBusinessCombinationsMember
696	Disclosure of detailed information about business combination [line items]	LineItems			ifrs-full:DisclosureOfBusinessCombinationsLineItems
697	Goodwill is deductible for income tax purposes	Concept (Monetary)	As Of	Debit	stn:GoodwillAndIntangibleAssetsExpectedDeductibleForTaxPurposes
698	Provisions	Concept (Monetary)	As Of	Credit	stn:ProvisionsForClaimsRecognisedAsOfAcquisitionDate
699	Provision for claims outstanding	Concept (Monetary)	As Of	Credit	stn:OutstandingProvisionsReassessedAndArisedBasedOnExpectedProbableOutcome
700	Gross revenue earned	Concept (Monetary)	For Period	Credit	ifrs-full:RevenueOfAcquiree
701	Acquisition-related costs	Concept (Monetary)	For Period	Debit	ifrs-full:AcquisitionrelatedCostsRecognisedAsExpenseForTransactionRecognisedSeparatelyFromAcquisitionOfAssetsAndAssumptionOfLiabilitiesInBusinessCombination
702	1086 - Disclosure - Business Acquisitions - Summary of Consideration of Business Combinations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureBusinessAcquisitionsSummaryOfConsiderationOfBusinessCombinations
703	Implied Table	Table	*	*	implied:Table
704	Disclosure of detailed information about business combination [abstract]	Abstract			ifrs-full:DisclosureOfBusinessCombinationsAbstract
705	Cash consideration (net of cash acquired)	Concept (Monetary)	For Period	Credit	ifrs-full:PortionOfConsiderationPaidReceivedConsistingOfCashAndCashEquivalents
706	Payments on notes payable from previous acquisitions	Concept (Monetary)	As Of	Credit	stn:PaymentsOnNotesPayableFromPreviousAcquisitions
707	Total net cash paid	Concept (Monetary)	For Period	Credit	ifrs-full:CashFlowsUsedInObtainingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
708	1087 - Disclosure - Business Acquisitions - Summary of Notes Payable in Business Combination (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureBusinessAcquisitionsSummaryOfNotesPayableInBusinessCombination
709	Implied Table	Table	*	*	implied:Table
710	Disclosure of Notes Payable in Business Combination [abstract]	Abstract			stn:DisclosureOfNotesPayableInBusinessCombinationAbstract
711	Balance, beginning of the year	Concept (Monetary)	As Of	Credit	stn:NotesPayableRecognisedInBusinessCombination
712	Additions for acquisitions in the year	Concept (Monetary)	For Period	Credit	stn:AdditionsForAcquisitionsOnNotesPayableRecognisedInBusinessCombination
713	Other adjustments	Concept (Monetary)	For Period	Credit	stn:OtherAdjustmentsOnNotesPayableRecognisedInBusinessCombination
714	Payments	Concept (Monetary)	For Period	Debit	stn:PaymentsOfNotesPayableRecognisedInBusinessCombination
715	Interest	Concept (Monetary)	For Period	Credit	stn:InterestOnNotesPayableRecognisedInBusinessCombination
716	Impact of foreign exchange	Concept (Monetary)	For Period	Credit	stn:IncreaseDecreaseThroughChangeInForeignExchangeOnNotesPayableRecognisedInBusinessCombination
717	Total notes payable	Concept (Monetary)	As Of	Credit	stn:NotesPayableRecognisedInBusinessCombination
718	1088 - Disclosure - Discontinued Operations and Disposition of Subsidiaries - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureDiscontinuedOperationsAndDispositionOfSubsidiariesAdditionalInformation
719	Disclosure of disposal of subsidiaries and discontinued operations [table]	Table	*	*	stn:DisclosureOfDisposalOfSubsidiariesAndDiscontinuedOperationsTable
720	Individual assets or cash-generating units [axis]	Axis			ifrs-full:IndividualAssetsOrCashgeneratingUnitsAxis
721	Entity's total for individual assets or cash-generating units [member]	Member			ifrs-full:EntitysTotalForIndividualAssetsOrCashgeneratingUnitsMember
722	Construction services group [member]	Member			stn:ConstructionServicesGroupMember
723	Continuing and discontinued operations [axis]	Axis			ifrs-full:ContinuingAndDiscontinuedOperationsAxis
724	Continuing operations [Member]	Member			ifrs-full:ContinuingOperationsMember
725	Disposal of major subsidiary [member]	Member			ifrs-full:DisposalOfMajorSubsidiaryMember
726	Discontinued operations [member]	Member			ifrs-full:DiscontinuedOperationsMember
727	Disclosure of disposal of subsidiaries and discontinued operations [line items]	LineItems			stn:DisclosureOfDisposalOfSubsidiariesAndDiscontinuedOperationsLineItems
728	Goodwill impairment charge	Concept (Monetary)	For Period	Debit	ifrs-full:ImpairmentLoss
729	Gross proceeds	Concept (Monetary)	For Period	Debit	stn:GrossProceedsFromDisposalOfSubsidiaries
730	Cash proceeds from the sale of subsidiary	Concept (Monetary)	For Period	Debit	ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities
731	Current tax expense	Concept (Monetary)	For Period	Debit	ifrs-full:CurrentTaxExpenseIncome
732	Deferred taxes	Concept (Monetary)	For Period	Debit	ifrs-full:DeferredTaxExpenseIncome
733	Repayment of long term debt	Concept (Monetary)	For Period	Credit	ifrs-full:RepaymentsOfNoncurrentBorrowings
734	1089 - Disclosure - Discontinued Operations and Disposition of Subsidiaries - Summary of Net Loss from Discontinued Operations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureDiscontinuedOperationsAndDispositionOfSubsidiariesSummaryOfNetLossFromDiscontinuedOperations
735	Disclosure of analysis of single amount of discontinued operations [table]	Table	*	*	ifrs-full:DisclosureOfAnalysisOfSingleAmountOfDiscontinuedOperationsTable
736	Continuing and discontinued operations [axis]	Axis			ifrs-full:ContinuingAndDiscontinuedOperationsAxis
737	Continuing operations [Member]	Member			ifrs-full:ContinuingOperationsMember
738	Construction services group [member]	Member			stn:ConstructionServicesGroupMember
739	Individual assets or cash-generating units [axis]	Axis			ifrs-full:IndividualAssetsOrCashgeneratingUnitsAxis
740	Entity's total for individual assets or cash-generating units [member]	Member			ifrs-full:EntitysTotalForIndividualAssetsOrCashgeneratingUnitsMember
741	Discontinued operations [member]	Member			ifrs-full:DiscontinuedOperationsMember
742	Disclosure of analysis of single amount of discontinued operations [line items]	LineItems			ifrs-full:DisclosureOfAnalysisOfSingleAmountOfDiscontinuedOperationsLineItems
743	Revenue	Concept (Monetary)	For Period	Credit	ifrs-full:Revenue
744	Expenses	Concept (Monetary)	For Period	Debit	ifrs-full:ExpenseByNature
745	Impairment of goodwill	Concept (Monetary)	For Period		ifrs-full:ImpairmentLossRecognisedInProfitOrLossGoodwill
746	Income before income taxes and discontinued operations	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLossBeforeTax
747	Income taxes on operating activities	Concept (Monetary)	For Period	Debit	ifrs-full:TaxExpenseRelatingToProfitLossFromOrdinaryActivitiesOfDiscontinuedOperations
748	Loss from operating activities, net of income taxes	Concept (Monetary)	For Period	Credit	ifrs-full:IncomeFromDiscontinuedOperationsAttributableToOwnersOfParent
749	Gain on disposal of discontinued operations before income taxes	Concept (Monetary)	For Period	Credit	stn:ProfitLossBeforeTaxDisposalOfDiscontinuedOperations
750	Income taxes on disposal of discontinued operations	Concept (Monetary)	For Period	Debit	ifrs-full:TaxExpenseRelatingToGainLossOnDiscontinuance
751	Loss on disposal of discontinued operations, net of income taxes	Concept (Monetary)	For Period	Credit	stn:ProfitLossFromDisposalOfDiscontinuedOperations
752	Net loss from discontinued operations	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitLossFromDiscontinuedOperations
753	1090 - Disclosure - Discontinued Operations and Disposition of Subsidiaries - Summary of Disposition of Subsidiary (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureDiscontinuedOperationsAndDispositionOfSubsidiariesSummaryOfDispositionOfSubsidiary
754	Disclosure of disposal of subsidiaries and discontinued operations [table]	Table	*	*	stn:DisclosureOfDisposalOfSubsidiariesAndDiscontinuedOperationsTable
755	Continuing and discontinued operations [axis]	Axis			ifrs-full:ContinuingAndDiscontinuedOperationsAxis
756	Continuing operations [Member]	Member			ifrs-full:ContinuingOperationsMember
757	Disposal of major subsidiary [member]	Member			ifrs-full:DisposalOfMajorSubsidiaryMember
758	Disclosure of disposal of subsidiaries and discontinued operations [line items]	LineItems			stn:DisclosureOfDisposalOfSubsidiariesAndDiscontinuedOperationsLineItems
759	Gross proceeds	Concept (Monetary)	For Period	Debit	stn:GrossProceedsFromDisposalOfSubsidiaries
760	Working capital adjustments	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseInWorkingCapital
761	Transaction costs	Concept (Monetary)	For Period	Credit	stn:DisposalGroupTransactionCost
762	Net proceeds from sale, net of cash sold	Concept (Monetary)	For Period	Debit	ifrs-full:ProceedsFromSalesOfInvestmentsOtherThanInvestmentsAccountedForUsingEquityMethod
763	Net assets disposed	Concept (Monetary)	For Period	Debit	ifrs-full:AssetsOtherThanCashOrCashEquivalentsInSubsidiaryOrBusinessesAcquiredOrDisposed2013
764	Cumulative exchange loss on translating foreign operations reclassified from equity	Concept (Monetary)	For Period	Debit	ifrs-full:ReclassificationAdjustmentsOnExchangeDifferencesOnTranslationNetOfTax
765	Gain on disposal of a subsidiary	Concept (Monetary)	For Period	Credit	ifrs-full:ProfitsLossesOnDisposalOfInvestmentsAndChangesInValueOfInvestments
766	1091 - Disclosure - Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureCashAndCashEquivalentsSummaryOfCashAndCashEquivalents
767	Implied Table	Table	*	*	implied:Table
768	Cash and cash equivalents [abstract]	Abstract			ifrs-full:CashAndCashEquivalentsAbstract
769	Cash	Concept (Monetary)	As Of	Debit	ifrs-full:Cash
770	Unrestricted investments	Concept (Monetary)	As Of	Debit	ifrs-full:ShorttermDepositsClassifiedAsCashEquivalents
771	Cash and cash equivalents	Concept (Monetary)	As Of	Debit	ifrs-full:CashAndCashEquivalents
772	1092 - Disclosure - Cash and Cash Equivalents - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureCashAndCashEquivalentsAdditionalInformation
773	Disclosure Of Cash And Cash Equivalents [table]	Table	*	*	stn:DisclosureOfCashAndCashEquivalentsTable
774	Business combinations [axis]	Axis			ifrs-full:BusinessCombinationsAxis
775	Entity's total for business combinations [member]	Member			ifrs-full:EntitysTotalForBusinessCombinationsMember
776	Business combinations [member]	Member			ifrs-full:BusinessCombinationsMember
777	Disclosure of cash and cash equivalents [line items]	LineItems			stn:DisclosureOfCashAndCashEquivalentsLineItems
778	Escrow account	Concept (Monetary)	As Of	Debit	ifrs-full:RestrictedCashAndCashEquivalents
779	1093 - Disclosure - Trade and Other Receivables - Schedule of Trade and Other Receivables (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureTradeAndOtherReceivablesScheduleOfTradeAndOtherReceivables
780	Implied Table	Table	*	*	implied:Table
781	Trade and other receivables [abstract]	Abstract			ifrs-full:TradeAndOtherReceivablesAbstract
782	Trade receivables, net of ECL of $1.5 (2017 - $2.1)	Concept (Monetary)	As Of	Debit	ifrs-full:TradeReceivables
783	Holdbacks, current	Concept (Monetary)	As Of	Debit	stn:HoldbacksCurrent
784	Lease inducements receivable	Concept (Monetary)	As Of	Debit	stn:LeaseInducementsReceivable
785	Other	Concept (Monetary)	As Of	Debit	ifrs-full:OtherReceivables
786	Trade and other receivables	Concept (Monetary)	As Of	Debit	ifrs-full:TradeAndOtherReceivables
787	1094 - Disclosure - Trade and Other Receivables - Schedule of Trade and Other Receivables (Parenthetical) (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureTradeAndOtherReceivablesScheduleOfTradeAndOtherReceivablesParenthetical
788	Implied Table	Table	*	*	implied:Table
789	Trade and other receivables [abstract]	Abstract			ifrs-full:TradeAndOtherReceivablesAbstract
790	Expected credit losses (ECLs)	Concept (Monetary)	As Of	Credit	ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
791	1095 - Disclosure - Trade and Other Receivables - Schedule of Gross Trade Receivables Aging Analysis (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureTradeAndOtherReceivablesScheduleOfGrossTradeReceivablesAgingAnalysis
792	Trade and Other Receivables [table]	Table	*	*	stn:TradeAndOtherReceivablesTable
793	Maturity [axis]	Axis			ifrs-full:MaturityAxis
794	Aggregated time bands [member]	Member			ifrs-full:AggregatedTimeBandsMember
795	1-30 Days [member]	Member			stn:OneToThirtyDaysMember
796	31-60 Days [member]	Member			stn:ThirtyOneToSixtyDaysMember
797	61-90 Days [member]	Member			stn:SixtyOneToNinetyDaysMember
798	91-120 Days [member]	Member			stn:NinetyOneDaysToOneTwentyDaysMember
799	121+ Days [member]	Member			stn:AboveOneTwentyOneDaysMember
800	Trade and other receivables [line items]	LineItems			stn:TradeAndOtherReceivablesLineItems
801	Trade receivables	Concept (Monetary)	As Of	Debit	stn:GrossTradeReceivables
802	1096 - Disclosure - Property and Equipment - Schedule of Property and Equipment (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipment
803	Disclosure of detailed information about property, plant and equipment [table]	Table	*	*	ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
804	Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis]	Axis			ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
805	Carrying amount [member]	Member			ifrs-full:CarryingAmountMember
806	Gross carrying amount [member]	Member			ifrs-full:GrossCarryingAmountMember
807	Accumulated depreciation and amortization [member]	Member			ifrs-full:AccumulatedDepreciationAndAmortisationMember
808	Classes of property, plant and equipment [axis]	Axis			ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
809	Property, plant and equipment [member]	Member			ifrs-full:PropertyPlantAndEquipmentMember
810	Engineering equipment [member]	Member			stn:EngineeringEquipmentMember
811	Office equipment [member]	Member			ifrs-full:OfficeEquipmentMember
812	Leasehold improvements [member]	Member			ifrs-full:LeaseholdImprovementsMember
813	Other [member]	Member			ifrs-full:OtherPropertyPlantAndEquipmentMember
814	Disclosure of detailed information about property, plant and equipment [line items]	LineItems			ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
815	Property plant and equipment	Concept (Monetary)	As Of	Debit	ifrs-full:PropertyPlantAndEquipment
816	Additions	Concept (Monetary)	For Period	Debit	ifrs-full:AdditionsOtherThanThroughBusinessCombinationsPropertyPlantAndEquipment
817	Depreciation - continuing operations	Concept (Monetary)	For Period	Debit	stn:DepreciationPropertyPlantAndEquipmentContinuingOperations
818	Additions arising on acquisitions	Concept (Monetary)	For Period	Debit	ifrs-full:AcquisitionsThroughBusinessCombinationsPropertyPlantAndEquipment
819	Depreciation - discontinued operations	Concept (Monetary)	For Period	Debit	stn:DepreciationPropertyPlantAndEquipmentDiscontinuedOperations
820	Disposals	Concept (Monetary)	For Period	Credit	ifrs-full:DisposalsPropertyPlantAndEquipment
821	Discontinued operations (note 8)	Concept (Monetary)	For Period	Credit	ifrs-full:DecreaseThroughLossOfControlOfSubsidiaryPropertyPlantAndEquipment
822	Transfers	Concept (Monetary)	For Period	Debit	ifrs-full:IncreaseDecreaseThroughTransfersPropertyPlantAndEquipment
823	Impact of foreign exchange	Concept (Monetary)	For Period	Debit	ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesPropertyPlantAndEquipment
824	Property plant and equipment	Concept (Monetary)	As Of	Debit	ifrs-full:PropertyPlantAndEquipment
825	1097 - Disclosure - Property and Equipment - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosurePropertyAndEquipmentAdditionalInformation
826	Disclosure of detailed information about property, plant and equipment [table]	Table	*	*	ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
827	Classes of property, plant and equipment [axis]	Axis			ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
828	Property, plant and equipment [member]	Member			ifrs-full:PropertyPlantAndEquipmentMember
829	Leasehold improvements [member]	Member			ifrs-full:LeaseholdImprovementsMember
830	Disclosure of detailed information about property, plant and equipment [line items]	LineItems			ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
831	Construction work in progress	Concept (Monetary)	As Of	Debit	ifrs-full:ConstructionInProgress
832	1098 - Disclosure - Goodwill - Schedule of Reconciliation of Changes in Goodwill (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureGoodwillScheduleOfReconciliationOfChangesInGoodwill
833	Disclosure of reconciliation of changes in goodwill [table]	Table	*	*	ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillTable
834	Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis]	Axis			ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
835	Carrying amount [member]	Member			ifrs-full:CarryingAmountMember
836	Gross carrying amount [member]	Member			ifrs-full:GrossCarryingAmountMember
837	Accumulated impairment [member]	Member			ifrs-full:AccumulatedImpairmentMember
838	Disclosure of reconciliation of changes in goodwill [line items]	LineItems			ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillLineItems
839	Goodwill	Concept (Monetary)	As Of	Debit	ifrs-full:Goodwill
840	Acquisitions	Concept (Monetary)	For Period	Debit	ifrs-full:AdditionalRecognitionGoodwill
841	Impairment of goodwill	Concept (Monetary)	For Period		ifrs-full:ImpairmentLossRecognisedInProfitOrLossGoodwill
842	Disposals	Concept (Monetary)	For Period	Credit	ifrs-full:GoodwillDerecognisedWithoutHavingPreviouslyBeenIncludedInDisposalGroupClassifiedAsHeldForSale
843	Impact of foreign exchange	Concept (Monetary)	For Period	Debit	ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesGoodwill
844	Goodwill	Concept (Monetary)	As Of	Debit	ifrs-full:Goodwill
845	1099 - Disclosure - Goodwill - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureGoodwillAdditionalInformation
846	Disclosure of information for cash-generating units [table]	Table	*	*	ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesTable
847	Cash-generating units [axis]	Axis			ifrs-full:IndividualAssetsOrCashgeneratingUnitsWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAxis
848	Entity's total for cash-generating units [member]	Member			ifrs-full:EntitysTotalForCashgeneratingUnitsMember
849	Consulting Services Global [member]	Member			stn:ConsultingServicesGlobalMember
850	Construction Services [member]	Member			stn:ConstructionServicesMember
851	Consulting Services United States [member]	Member			stn:ConsultingServicesUnitedStatesMember
852	Range [axis]	Axis			ifrs-full:RangeAxis
853	Ranges [member]	Member			ifrs-full:RangesMember
854	Top of range [member]	Member			ifrs-full:TopOfRangeMember
855	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
856	Individual assets or cash-generating units [axis]	Axis			ifrs-full:IndividualAssetsOrCashgeneratingUnitsAxis
857	Entity's total for individual assets or cash-generating units [member]	Member			ifrs-full:EntitysTotalForIndividualAssetsOrCashgeneratingUnitsMember
858	Construction services group [member]	Member			stn:ConstructionServicesGroupMember
859	Continuing and discontinued operations [axis]	Axis			ifrs-full:ContinuingAndDiscontinuedOperationsAxis
860	Continuing operations [Member]	Member			ifrs-full:ContinuingOperationsMember
861	Discontinued operations [member]	Member			ifrs-full:DiscontinuedOperationsMember
862	Disclosure of information for cash-generating units [line items]	LineItems			ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesLineItems
863	Number of cash generating units	Concept (Integer)	For Period		stn:NumberOfCashGeneratingUnit
864	Goodwill impairment charge	Concept (Monetary)	For Period	Debit	ifrs-full:ImpairmentLoss
865	Goodwill disposed	Concept (Monetary)	For Period	Credit	ifrs-full:GoodwillDerecognisedWithoutHavingPreviouslyBeenIncludedInDisposalGroupClassifiedAsHeldForSale
866	Discounted Rate	Concept (Percent)	As Of		ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
867	Description of basis on which units recoverable amount has been determined	Concept (Text/String)	For Period		ifrs-full:DescriptionOfBasisOnWhichUnitsRecoverableAmountHasBeenDetermined
868	Description of level of fair value hierarchy within which fair value measurement is categorised	Concept (Text/String)	For Period		ifrs-full:DescriptionOfLevelOfFairValueHierarchyWithinWhichFairValueMeasurementIsCategorised
869	Description of projection	Concept (Text/String)	For Period		ifrs-full:ExplanationOfPeriodOverWhichManagementHasProjectedCashFlows
870	Percentage of growth rate	Concept (Percent)	As Of		ifrs-full:DescriptionOfGrowthRateUsedToExtrapolateCashFlowProjections
871	1100 - Disclosure - Goodwill - Schedule of Goodwill Allocated (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureGoodwillScheduleOfGoodwillAllocated
872	Disclosure of information for cash-generating units [table]	Table	*	*	ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesTable
873	Cash-generating units [axis]	Axis			ifrs-full:IndividualAssetsOrCashgeneratingUnitsWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAxis
874	Entity's total for cash-generating units [member]	Member			ifrs-full:EntitysTotalForCashgeneratingUnitsMember
875	Consulting Services Canada [member]	Member			stn:ConsultingServicesCanadaMember
876	Consulting Services United States [member]	Member			stn:ConsultingServicesUnitedStatesMember
877	Consulting Services Global [member]	Member			stn:ConsultingServicesGlobalMember
878	Construction Services [member]	Member			stn:ConstructionServicesMember
879	Disclosure of information for cash-generating units [line items]	LineItems			ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesLineItems
880	Goodwill	Concept (Monetary)	As Of	Debit	ifrs-full:Goodwill
881	1101 - Disclosure - Goodwill - Summary of Most Sensitive Key Assumptions Used for CGUs (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureGoodwillSummaryOfMostSensitiveKeyAssumptionsUsedForCGUs
882	Disclosure of information for cash-generating units [table]	Table	*	*	ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesTable
883	Cash-generating units [axis]	Axis			ifrs-full:IndividualAssetsOrCashgeneratingUnitsWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesAxis
884	Entity's total for cash-generating units [member]	Member			ifrs-full:EntitysTotalForCashgeneratingUnitsMember
885	Consulting Services Global [member]	Member			stn:ConsultingServicesGlobalMember
886	Range [axis]	Axis			ifrs-full:RangeAxis
887	Ranges [member]	Member			ifrs-full:RangesMember
888	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
889	Top of range [member]	Member			ifrs-full:TopOfRangeMember
890	Disclosure of information for cash-generating units [line items]	LineItems			ifrs-full:DisclosureOfInformationForIndividualAssetOrCashgeneratingUnitWithSignificantAmountOfGoodwillOrIntangibleAssetsWithIndefiniteUsefulLivesLineItems
891	Operating margin rates	Concept (Percent)	For Period		stn:OperatingMarginRateAppliedToCashFlowProjections
892	After tax discount rate	Concept (Percent)	As Of		ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
893	Terminal growth rate	Concept (Percent)	As Of		ifrs-full:DescriptionOfGrowthRateUsedToExtrapolateCashFlowProjections
894	Non-cash working capital rates	Concept (Percent)	For Period		stn:NoncashWorkingCapitalRateAppliedToCashFlowProjections
895	Average annual net revenue growth rate (2019-2023)	Concept (Percent)	As Of		stn:RevenueGrowthRates
896	1102 - Disclosure - Intangible Assets - Summary of Intangible Assets (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIntangibleAssetsSummaryOfIntangibleAssets
897	Disclosure of detailed information about intangible assets [table]	Table	*	*	ifrs-full:DisclosureOfIntangibleAssetsTable
898	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
899	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
900	Innovyze, Inc. [member]	Member			stn:InnovyzeIncMember
901	Other [member]	Member			ifrs-full:OtherRelatedPartiesMember
902	Classes of intangible assets other than goodwill [axis]	Axis			ifrs-full:ClassesOfIntangibleAssetsOtherThanGoodwillAxis
903	Intangible assets other than goodwill [member]	Member			ifrs-full:IntangibleAssetsOtherThanGoodwillMember
904	Client relationships [member]	Member			ifrs-full:CustomerrelatedIntangibleAssetsMember
905	Contract backlog [member]	Member			stn:ContractBacklogMember
906	Software [member]	Member			ifrs-full:ComputerSoftwareMember
907	Other [member]	Member			ifrs-full:OtherIntangibleAssetsMember
908	Lease disadvantages [member]	Member			stn:LeaseDisadvantagesMember
909	Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis]	Axis			ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
910	Carrying amount [member]	Member			ifrs-full:CarryingAmountMember
911	Gross carrying amount [member]	Member			ifrs-full:GrossCarryingAmountMember
912	Accumulated depreciation and amortization [member]	Member			ifrs-full:AccumulatedDepreciationAndAmortisationMember
913	Methods of generation [axis]	Axis			ifrs-full:MethodsOfGenerationAxis
914	Methods of generation [member]	Member			ifrs-full:MethodsOfGenerationMember
915	Not internally generated [member]	Member			ifrs-full:NotInternallyGeneratedMember
916	Disclosure of detailed information about intangible assets [line Items]	LineItems			ifrs-full:DisclosureOfIntangibleAssetsLineItems
917	Beginning Balance	Concept (Monetary)	As Of	Debit	ifrs-full:IntangibleAssetsOtherThanGoodwill
918	Additions	Concept (Monetary)	For Period	Debit	ifrs-full:AdditionsOtherThanThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
919	Amortization - continuing operations	Concept (Monetary)	For Period		stn:AmortisationIntangibleAssetsOtherThanGoodwillContinuingOperations
920	Amortization - discontinued operations	Concept (Monetary)	For Period		stn:AmortisationIntangibleAssetsOtherThanGoodwillDiscontinuedOperations
921	Additions arising on acquisitions	Concept (Monetary)	For Period	Debit	ifrs-full:AcquisitionsThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
922	Disposals	Concept (Monetary)	For Period	Credit	ifrs-full:DisposalsIntangibleAssetsOtherThanGoodwill
923	Discontinued operations (note 8)	Concept (Monetary)	For Period	Credit	ifrs-full:DecreaseThroughLossOfControlOfSubsidiaryIntangibleAssetsOtherThanGoodwill
924	Removal of fully amortized assets	Concept (Monetary)	For Period	Credit	ifrs-full:RetirementsIntangibleAssetsOtherThanGoodwill
925	Impact of foreign exchange	Concept (Monetary)	For Period	Debit	ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesIntangibleAssetsOtherThanGoodwill
926	Beginning Balance	Concept (Monetary)	As Of	Debit	ifrs-full:IntangibleAssetsOtherThanGoodwill
927	1103 - Disclosure - Intangible Assets - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIntangibleAssetsAdditionalInformation
928	Disclosure of detailed information about intangible assets [table]	Table	*	*	ifrs-full:DisclosureOfIntangibleAssetsTable
929	Classes of intangible assets other than goodwill [axis]	Axis			ifrs-full:ClassesOfIntangibleAssetsOtherThanGoodwillAxis
930	Intangible assets other than goodwill [member]	Member			ifrs-full:IntangibleAssetsOtherThanGoodwillMember
931	Software licenses [member]	Member			stn:SoftwareLicensesMember
932	Disclosure of detailed information about intangible assets [line Items]	LineItems			ifrs-full:DisclosureOfIntangibleAssetsLineItems
933	Non cash portion of financial leases additions	Concept (Monetary)	As Of	Credit	stn:NonCashPortionOfSoftwareAdditions
934	Finance leases with a net book value	Concept (Monetary)	As Of	Debit	ifrs-full:RecognisedFinanceLeaseAsAssets
935	1104 - Disclosure - Other Assets - Schedule of Other Assets (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureOtherAssetsScheduleOfOtherAssets
936	Disclosure of Other Assets [table]	Table	*	*	stn:DisclosureOfOtherAssetsTable
937	Classes of assets [axis]	Axis			ifrs-full:ClassesOfAssetsAxis
938	Assets [member]	Member			ifrs-full:ClassesOfAssetsMember
939	Other assets [member]	Member			ifrs-full:OtherAssetsMember
940	Classes of financial assets [axis]	Axis			ifrs-full:ClassesOfFinancialAssetsAxis
941	Financial assets, class [member]	Member			ifrs-full:FinancialAssetsMember
942	Investments held for self-insured liabilities [member]	Member			stn:InvestmentsHeldForSelfInsuredLiabilitiesMember
943	Holdbacks on long-term contracts [member]	Member			stn:HoldbacksOnLongTermContractMember
944	Indemnifications [member]	Member			stn:IndemnificationsMember
945	Other [member]	Member			stn:OtherMember
946	Classes of other non financial assets [axis]	Axis			stn:ClassesOfOtherNonFinancialAssetsAxis
947	Classes of other non financial assets [domain]	Member			stn:ClassesOfOtherNonFinancialAssetsDomain
948	Investment tax credits [member]	Member			stn:InvestmentTaxCreditsMember
949	Transaction costs on long term debt [member]	Member			stn:TransactionCostsOnLongTermDebtMember
950	Deferred contract costs [member]	Member			stn:DeferredContractCostsMember
951	Disclosure of other assets [line items]	LineItems			stn:DisclosureOfOtherAssetsLineItems
952	Other financial assets	Concept (Monetary)	As Of	Debit	ifrs-full:OtherFinancialAssets
953	Other non-financial assets	Concept (Monetary)	As Of	Debit	ifrs-full:OtherNonfinancialAssets
954	Other Assets	Concept (Monetary)	As Of	Debit	ifrs-full:OtherAssets
955	Less current portion - financial	Concept (Monetary)	As Of	Debit	ifrs-full:OtherCurrentFinancialAssets
956	Less current portion - non-financial	Concept (Monetary)	As Of	Debit	ifrs-full:OtherCurrentNonfinancialAssets
957	Long-term portion	Concept (Monetary)	As Of	Debit	ifrs-full:OtherNoncurrentAssets
958	1105 - Disclosure - Other Assets - Disclosure of Fair Value and Amortized Cost (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureOtherAssetsDisclosureOfFairValueAndAmortizedCost
959	Disclosure Of Investments Held For Self Insured Liabilities At Fair Value And Amortized Cost [table]	Table	*	*	stn:DisclosureOfInvestmentsHeldForSelfInsuredLiabilitiesAtFairValueAndAmortizedCostTable
960	Classes of financial assets [axis]	Axis			ifrs-full:ClassesOfFinancialAssetsAxis
961	Financial assets, class [member]	Member			ifrs-full:FinancialAssetsMember
962	Bonds [member]	Member			stn:BondMember
963	Equity securities [member]	Member			ifrs-full:EquityInvestmentsMember
964	Disclosure of investments held for self insured liabilities at fair value and amortized cost [line items]	LineItems			stn:DisclosureOfInvestmentsHeldForSelfInsuredLiabilitiesAtFairValueAndAmortizedCostLineItems
965	Fair Value	Concept (Monetary)	As Of	Debit	ifrs-full:OtherFinancialAssets
966	Amortized Cost/Cost	Concept (Monetary)	As Of	Debit	stn:OtherFinancialAssetAtAmortisedCost
967	1106 - Disclosure - Other Assets - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureOtherAssetsAdditionalInformation
968	Disclosure Of Investments Held For Self Insured Liabilities Maturity Of Bond Portfolio At Fair Value [table]	Table	*	*	stn:DisclosureOfInvestmentsHeldForSelfInsuredLiabilitiesMaturityOfBondPortfolioAtFairValueTable
969	Range [axis]	Axis			ifrs-full:RangeAxis
970	Ranges [member]	Member			ifrs-full:RangesMember
971	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
972	Top of range [member]	Member			ifrs-full:TopOfRangeMember
973	Disclosure of investments held for self insured liabilities maturity of bond portfolio at fair value [line items]	LineItems			stn:DisclosureOfInvestmentsHeldForSelfInsuredLiabilitiesMaturityOfBondPortfolioAtFairValueLineItems
974	Bonds interest rate	Concept (Percent)	For Period		stn:BondsInterestRatePercentage
975	Changes in provisions and indemnification assets	Concept (Monetary)	As Of	Debit	stn:IncreaseInProvisionsAndIndemnificationAssets
976	1107 - Disclosure - Other Assets - Disclosure of the Bond Portfolio Stated at Fair Value (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureOtherAssetsDisclosureOfTheBondPortfolioStatedAtFairValue
977	Disclosure of maturity analysis for financial assets held for managing liquidity risk [table]	Table	*	*	ifrs-full:DisclosureOfMaturityAnalysisForFinancialAssetsHeldForManagingLiquidityRiskTable
978	Maturity [axis]	Axis			ifrs-full:MaturityAxis
979	Aggregated time bands [member]	Member			ifrs-full:AggregatedTimeBandsMember
980	Within one year [member]	Member			ifrs-full:NotLaterThanOneYearMember
981	2018 to 2022 [member]	Member			ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
982	More than five years [member]	Member			ifrs-full:LaterThanFiveYearsMember
983	Classes of financial assets [axis]	Axis			ifrs-full:ClassesOfFinancialAssetsAxis
984	Financial assets, class [member]	Member			ifrs-full:FinancialAssetsMember
985	Bonds [member]	Member			stn:BondMember
986	Disclosure of maturity analysis for financial assets held for managing liquidity risk [line items]	LineItems			ifrs-full:DisclosureOfMaturityAnalysisForFinancialAssetsHeldForManagingLiquidityRiskLineItems
987	Maturity of bond portfolio, stated fair value	Concept (Monetary)	As Of	Debit	stn:FairValueOfOtherFinancialAssetsMaturityAmount
988	1108 - Disclosure - Trade and Other Payables - Summary of Trade and Other Payables (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureTradeAndOtherPayablesSummaryOfTradeAndOtherPayables
989	Implied Table	Table	*	*	implied:Table
990	Trade and other payables [abstract]	Abstract			ifrs-full:TradeAndOtherPayablesAbstract
991	Trade accounts payable	Concept (Monetary)	As Of	Credit	ifrs-full:TradeAndOtherPayablesToTradeSuppliers
992	Employee and payroll liabilities	Concept (Monetary)	As Of	Credit	stn:EmployeeAndPayrollLiabilities
993	Accrued liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:Accruals
994	Trade and other payables	Concept (Monetary)	As Of	Credit	ifrs-full:TradeAndOtherPayables
995	1109 - Disclosure - Long-Term Debt - Summary of Long Term Debt (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureLongTermDebtSummaryOfLongTermDebt
996	Disclosure of detailed information about borrowings [table]	Table	*	*	ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
997	Borrowings by name [axis]	Axis			ifrs-full:BorrowingsByNameAxis
998	Borrowings by name [member]	Member			ifrs-full:BorrowingsByNameMember
999	Notes payable [member]	Member			stn:NotesPayableMember
1000	Revolving credit facilities [member]	Member			stn:RevolvingCreditFacility1Member
1001	Term loan [member]	Member			stn:TermLoanMember
1002	Finance lease obligations [member]	Member			stn:FinanceLeaseObligationsMember
1003	Disclosure of detailed information about borrowings [line items]	LineItems			ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
1004	Borrowings	Concept (Monetary)	As Of	Credit	ifrs-full:Borrowings
1005	Less current portion	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentPortionOfLongtermBorrowings
1006	Long-term portion	Concept (Monetary)	As Of	Credit	ifrs-full:LongtermBorrowings
1007	1110 - Disclosure - Long-Term Debt - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureLongTermDebtAdditionalInformation
1008	Disclosure of detailed information about borrowings [table]	Table	*	*	ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
1009	Borrowings by name [axis]	Axis			ifrs-full:BorrowingsByNameAxis
1010	Borrowings by name [member]	Member			ifrs-full:BorrowingsByNameMember
1011	Revolving credit facilities [member]	Member			stn:RevolvingCreditFacility1Member
1012	Notes payable [member]	Member			stn:NotesPayableMember
1013	Term loan [member]	Member			stn:TermLoanMember
1014	Term loan tranche B [member]	Member			stn:TermLoanTranchebMember
1015	Term loan tranche C [member]	Member			stn:TermLoanTranchecMember
1016	Tranche A [member]	Member			stn:TrancheAMember
1017	Finance lease obligations [member]	Member			stn:FinanceLeaseObligationsMember
1018	Past due status [axis]	Axis			ifrs-full:PastDueStatusAxis
1019	Past due status [member]	Member			ifrs-full:PastDueStatusMember
1020	Expire before two thousand twenty [member]	Member			stn:ExpireBeforeTwoThousandTwentyMember
1021	Expire after two thousand twenty [member]	Member			stn:ExpireAfterTwoThousandTwentyMember
1022	Range [axis]	Axis			ifrs-full:RangeAxis
1023	Ranges [member]	Member			ifrs-full:RangesMember
1024	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
1025	Top of range [member]	Member			ifrs-full:TopOfRangeMember
1026	Classes of financial instruments [axis]	Axis			ifrs-full:ClassesOfFinancialInstrumentsAxis
1027	Financial instruments, class [member]	Member			ifrs-full:ClassesOfFinancialInstrumentsMember
1028	US funds [member]	Member			stn:UnitedStatesFundMember
1029	Foreign currencies [member]	Member			stn:ForeignCurrenciesMember
1030	Canadian funds [member]	Member			stn:CanadianFundMember
1031	Types of interest rates [axis]	Axis			ifrs-full:TypesOfInterestRatesAxis
1032	Interest rate types [member]	Member			ifrs-full:InterestRateTypesMember
1033	Canadian prime rate and US base rate [member]	Member			stn:CanadianPrimeRateAndUsBaseRateMember
1034	Disclosure of detailed information about borrowings [line items]	LineItems			ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsLineItems
1035	Weighted average rate of interest	Concept (Percent)	As Of		stn:WeightedAverageInterestRate
1036	Aggregate maturity value of notes	Concept (Monetary)	As Of	Credit	stn:AggregateMaturityValueOfNotes
1037	Carrying amount of notes payable	Concept (Monetary)	As Of	Credit	stn:CarryingAmountOfNotesPayable
1038	Revolving credit facilities amount	Concept (Monetary)	As Of	Credit	stn:LineOfCreditFacilityMaximumBorrowingsCapacity
1039	Number of tranches	Concept (Integer)	For Period		stn:NumberOfTranches
1040	Revolving credit facilities maturity term	Concept (xbrli:durationItemType)	For Period		stn:LineOfCreditMaturityPeriod
1041	Additional revolving credit facilities amount	Concept (Monetary)	As Of	Credit	stn:LineOfCreditFacilityAdditionalBorrowingsCapacity
1042	Gain on modification of revolving credit facilities	Concept (Monetary)	For Period	Debit	stn:GainOnRevolvingCreditFacilitiesModification
1043	Agreement expiry date	Concept (Date)	For Period		stn:AgreementExpiryDate
1044	Drawn borrowing facilities	Concept (Monetary)	As Of	Credit	stn:DrawnBorrowingFacilities
1045	Borrowing, interest rate basis	Concept (Text/String)	For Period		ifrs-full:BorrowingsInterestRateBasis
1046	Revolving credit facility payable	Concept (Monetary)	As Of	Credit	stn:RevolvingCreditFacilityPayableAmount
1047	Credit facility average interest rate	Concept (Percent)	For Period		stn:CreditFacilityAverageInterestRate
1048	Letter of credit issued	Concept (Monetary)	For Period	Credit	stn:LettersOfCreditIssuedAmount
1049	Letter of credit outstanding	Concept (Monetary)	As Of	Credit	stn:LettersOfCreditOutstandingAmount1
1050	Unused capacity amount	Concept (Monetary)	As Of	Credit	stn:LineOfCreditFacilityRemainingBorrowingCapacity1
1051	Letter of credit issued and outstanding in addition	Concept (Monetary)	For Period	Credit	stn:LettersOfCreditIssuedAndOutstandingInAddition
1052	Bonds issued under surety facilities	Concept (Monetary)	As Of	Credit	ifrs-full:BondsIssued
1053	Borrowings, interest rate	Concept (Percent)	As Of		ifrs-full:BorrowingsInterestRate
1054	1111 - Disclosure - Long-Term Debt - Future Minimum Lease Payments and Present Value of the Net Minimum Lease Payments under Finance Leases (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureLongTermDebtFutureMinimumLeasePaymentsAndPresentValueOfTheNetMinimumLeasePaymentsUnderFinanceLeases
1055	Disclosure of finance lease and operating lease by lessee [table]	Table	*	*	ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeTable
1056	Maturity [axis]	Axis			ifrs-full:MaturityAxis
1057	Aggregated time bands [member]	Member			ifrs-full:AggregatedTimeBandsMember
1058	Within one year [member]	Member			ifrs-full:NotLaterThanOneYearMember
1059	2018 to 2022 [member]	Member			ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
1060	Disclosure of finance lease and operating lease by lessee [Line Items]	LineItems			ifrs-full:DisclosureOfFinanceLeaseAndOperatingLeaseByLesseeLineItems
1061	Total minimum lease payments	Concept (Monetary)	As Of	Credit	ifrs-full:MinimumFinanceLeasePaymentsPayable
1062	Less amounts representing finance charges	Concept (Monetary)	As Of	Credit	ifrs-full:FutureFinanceChargeOnFinanceLease
1063	Present value of minimum lease payments	Concept (Monetary)	As Of	Credit	ifrs-full:MinimumFinanceLeasePaymentsPayableAtPresentValue
1064	1112 - Disclosure - Provisions - Summary of Provisions (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureProvisionsSummaryOfProvisions
1065	Disclosure of other provisions [table]	Table	*	*	ifrs-full:DisclosureOfOtherProvisionsTable
1066	Classes of other provisions [axis]	Axis			ifrs-full:ClassesOfProvisionsAxis
1067	Other provisions [member]	Member			ifrs-full:OtherProvisionsMember
1068	Self-insured liabilities provision [member]	Member			stn:SelfInsuredLiabilitiesProvisionMember
1069	Claims provision [member]	Member			stn:ProvisionForClaimsMember
1070	Onerous contracts provision [member]	Member			ifrs-full:OnerousContractsProvisionMember
1071	Expected project loss [member]	Member			stn:ExpectedProjectLossMember
1072	Disclosure of other provisions [Line Items]	LineItems			ifrs-full:DisclosureOfOtherProvisionsLineItems
1073	Provision, beginning of the year	Concept (Monetary)	As Of	Credit	ifrs-full:OtherProvisions
1074	Current year provisions	Concept (Monetary)	For Period	Credit	ifrs-full:AdditionalProvisionsOtherProvisions
1075	Acquisitions	Concept (Monetary)	For Period	Credit	ifrs-full:AcquisitionsThroughBusinessCombinationsOtherProvisions
1076	Paid or otherwise settled	Concept (Monetary)	For Period	Debit	ifrs-full:ProvisionUsedOtherProvisions
1077	Impact of foreign exchange	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesOtherProvisions
1078	Provisions, end of the year	Concept (Monetary)	As Of	Credit	ifrs-full:OtherProvisions
1079	Less current portion	Concept (Monetary)	As Of	Credit	ifrs-full:OtherShorttermProvisions
1080	Long-term portion	Concept (Monetary)	As Of	Credit	ifrs-full:OtherLongtermProvisions
1081	1113 - Disclosure - Provisions - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureProvisionsAdditionalInformation
1082	Disclosure of Provisions [table]	Table	*	*	stn:DisclosureOfProvisionsTable
1083	Range [axis]	Axis			ifrs-full:RangeAxis
1084	Ranges [member]	Member			ifrs-full:RangesMember
1085	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
1086	Top of range [member]	Member			ifrs-full:TopOfRangeMember
1087	Classes of other provisions [axis]	Axis			ifrs-full:ClassesOfProvisionsAxis
1088	Other provisions [member]	Member			ifrs-full:OtherProvisionsMember
1089	Lease exit liability [member]	Member			stn:LeaseExitLiabilityMember
1090	Disclosure of Provisions [line items]	LineItems			stn:DisclosureOfProvisionsLineItems
1091	Cash outflows for existing provisions expected period	Concept (Text/String)	For Period		ifrs-full:DescriptionOfExpectedTimingOfOutflowsOtherProvisions
1092	Current year provisions	Concept (Monetary)	For Period	Credit	ifrs-full:AdditionalProvisionsOtherProvisions
1093	1114 - Disclosure - Employee Defined Benefit Obligations - Summary of Employee Defined Benefit Obligations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfEmployeeDefinedBenefitObligations
1094	Disclosure of defined benefit plans [table]	Table	*	*	ifrs-full:DisclosureOfDefinedBenefitPlansTable
1095	Characteristics of defined benefit plans [axis]	Axis			ifrs-full:CharacteristicsOfDefinedBenefitPlansAxis
1096	Characteristics of defined benefit plans [member]	Member			ifrs-full:CharacteristicsOfDefinedBenefitPlansMember
1097	Pension defined benefit plans [member]	Member			ifrs-full:PensionDefinedBenefitPlansMember
1098	Post employment benefit plans [member]	Member			stn:PostEmploymentBenefitPlansMember
1099	Disclosure of defined benefit plans [line items]	LineItems			ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
1100	Net defined benefit pension asset	Concept (Monetary)	As Of	Debit	ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan
1101	Net defined benefit pension liability/ End of employment benefit plans	Concept (Monetary)	As Of	Credit	ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan
1102	1115 - Disclosure - Employee Defined Benefit Obligations - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsAdditionalInformation
1103	Disclosure of defined benefit plans [table]	Table	*	*	ifrs-full:DisclosureOfDefinedBenefitPlansTable
1104	Net defined benefit liability (asset) [axis]	Axis			ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1105	Net defined benefit liability (asset) [member]	Member			ifrs-full:NetDefinedBenefitLiabilityAssetMember
1106	Defined benefit obligation [member]	Member			ifrs-full:PresentValueOfDefinedBenefitObligationMember
1107	Non-adjusting events after reporting period [axis]	Axis			ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
1108	Non-adjusting events after reporting period [member]	Member			ifrs-full:NonadjustingEventsMember
1109	Defined benefit pension plans contribution [member]	Member			stn:DefinedBenefitPensionPlansContributionMember
1110	Continuing and discontinued operations [axis]	Axis			ifrs-full:ContinuingAndDiscontinuedOperationsAxis
1111	Continuing operations [Member]	Member			ifrs-full:ContinuingOperationsMember
1112	Continuing Operations1[member]	Member			stn:ContinuingOperations1Member
1113	Discontinued operations [member]	Member			ifrs-full:DiscontinuedOperationsMember
1114	Disclosure of defined benefit plans [line items]	LineItems			ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
1115	Number of employer-appointed trustee	Concept (Integer)	For Period		stn:NumberOfEmployerAppointedTrustee
1116	Amount expected to contribute to pension plan by company	Concept (Monetary)	For Period	Credit	ifrs-full:EstimateOfContributionsExpectedToBePaidToPlan
1117	Past service cost	Concept (Monetary)	For Period	Credit	ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
1118	Percentage of plans' assets invested in mutual funds and exchange-traded funds or held in cash	Concept (Percent)	For Period		stn:PercentageOfPlanAssetInSecuritiesOrHeldInCash
1119	Percentage of plans' assets held in annuity policies	Concept (Percent)	For Period		stn:PercentageOfPlanAssetInAnnuityPolicies
1120	Weighted average duration of defined benefit obligation	Concept (Decimal)	For Period		ifrs-full:WeightedAverageDurationOfDefinedBenefitObligation
1121	1116 - Disclosure - Employee Defined Benefit Obligations - Summary of Reconciliation for Net Defined Benefit Liability (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfReconciliationForNetDefinedBenefitLiability
1122	Disclosure of net defined benefit liability (asset) [table]	Table	*	*	ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1123	Net defined benefit liability (asset) [axis]	Axis			ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1124	Net defined benefit liability (asset) [member]	Member			ifrs-full:NetDefinedBenefitLiabilityAssetMember
1125	Defined benefit obligation [member]	Member			ifrs-full:PresentValueOfDefinedBenefitObligationMember
1126	Fair value of plan assets [member]	Member			ifrs-full:PlanAssetsMember
1127	Characteristics of defined benefit plans [axis]	Axis			ifrs-full:CharacteristicsOfDefinedBenefitPlansAxis
1128	Characteristics of defined benefit plans [member]	Member			ifrs-full:CharacteristicsOfDefinedBenefitPlansMember
1129	Pension defined benefit plans [member]	Member			ifrs-full:PensionDefinedBenefitPlansMember
1130	Disclosure of net defined benefit liability (asset) [Line Items]	LineItems			ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1131	Balance, beginning of the year	Concept (Monetary)	As Of	Credit	ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1132	Net defined benefit asset	Concept (Monetary)	As Of	Debit	ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan
1133	Acquisition of PBA	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughBusinessCombinationsAndDisposalsNetDefinedBenefitLiabilityAsset
1134	Net defined benefit liability	Concept (Monetary)	As Of	Credit	ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan
1135	Included in pre-tax profit or loss	Abstract			stn:CostOfNetDefinedBenefitLiabilityAssetIncludedInProfitOrLossAbstract
1136	Interest expense (income)	Concept (Monetary)	For Period	Credit	ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
1137	Past service cost	Concept (Monetary)	For Period	Credit	ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
1138	Administrative expenses paid by the Plans	Concept (Monetary)	For Period	Credit	stn:AdministrativeExpenseNetDefinedBenefitLiabilityAsset
1139	Net defined benefit liability asset included in profit or loss	Concept (Monetary)	For Period	Credit	stn:NetDefinedBenefitLiabilityAssetIncludedInProfitOrLoss
1140	Included in other comprehensive income	Abstract			ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAssetAbstract
1141	Return on the plan assets (excluding interest income)	Concept (Monetary)	For Period	Debit	ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
1142	Actuarial (gains) losses arising from:	Abstract			stn:ActuarialGainsLossesArisingFromNetDefinedBenefitLiabilityAssetAbstract
1143	Changes in demographic assumptions	Concept (Monetary)	For Period	Debit	ifrs-full:ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
1144	Changes in financial assumptions	Concept (Monetary)	For Period	Debit	ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
1145	Experience adjustments	Concept (Monetary)	For Period	Debit	ifrs-full:ActuarialGainsLossesArisingFromExperienceAdjustmentsNetDefinedBenefitLiabilityAsset
1146	Effect of movement in exchange rates	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughChangesInForeignExchangeRatesNetDefinedBenefitLiabilityAsset
1147	Net defined benefit liability asset included in other comprehensive income	Concept (Monetary)	For Period	Debit	ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAsset
1148	Other	Abstract			stn:OtherNetDefinedBenefitLiabilityAssetAbstract
1149	Benefits paid	Concept (Monetary)	For Period	Debit	ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
1150	Contributions by employer	Concept (Monetary)	For Period	Debit	ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
1151	Other net defined benefit liability asset	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughOtherChangesNetDefinedBenefitLiabilityAsset
1152	Balance, end of the year	Concept (Monetary)	As Of	Credit	ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1153	1117 - Disclosure - Employee Defined Benefit Obligations - Summary of Net Defined Benefit Asset (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfNetDefinedBenefitAsset
1154	Implied Table	Table	*	*	implied:Table
1155	Disclosure of defined benefit plans [abstract]	Abstract			ifrs-full:DisclosureOfDefinedBenefitPlansAbstract
1156	Continuing operations - administrative and marketing expenses	Concept (Monetary)	For Period	Credit	stn:NetDefinedBenefitLiabilityAssetIncludedInProfitOrLossContinuingOperations
1157	Discontinued operations	Concept (Monetary)	For Period	Credit	stn:NetDefinedBenefitLiabilityAssetIncludedInProfitOrLossDiscontinuingOperations
1158	Net defined benefit liability asset included in profit or loss	Concept (Monetary)	For Period	Credit	stn:NetDefinedBenefitLiabilityAssetIncludedInProfitOrLoss
1159	1118 - Disclosure - Employee Defined Benefit Obligations - Summary of Major Categories of Plan Assets, Measured at Fair Value (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfMajorCategoriesOfPlanAssetsMeasuredAtFairValue
1160	Disclosure of fair value of plan assets [table]	Table	*	*	ifrs-full:DisclosureOfFairValueOfPlanAssetsTable
1161	Levels of fair value hierarchy [axis]	Axis			ifrs-full:LevelsOfFairValueHierarchyAxis
1162	All levels of fair value hierarchy [member]	Member			ifrs-full:AllLevelsOfFairValueHierarchyMember
1163	Quoted prices in active markets for identical items [member]	Member			ifrs-full:Level1OfFairValueHierarchyMember
1164	Unquoted investment [member]	Member			ifrs-full:Level2And3OfFairValueHierarchyMember
1165	Disclosure of fair value of plan assets [Line Items]	LineItems			ifrs-full:DisclosureOfFairValueOfPlanAssetsLineItems
1166	Annuity policies	Concept (Monetary)	As Of	Debit	stn:AnnuityPoliciesAmountContributedToFairValueOfPlanAssets
1167	Equities and property	Concept (Monetary)	As Of	Debit	stn:EquityInstrumentsAndPropertyAmountContributedToFairValueOfPlanAssets
1168	Corporate bonds and fixed income	Concept (Monetary)	As Of	Debit	ifrs-full:DebtInstrumentsAmountContributedToFairValueOfPlanAssets
1169	Cash and cash equivalents	Concept (Monetary)	As Of	Debit	ifrs-full:CashAndCashEquivalentsAmountContributedToFairValueOfPlanAssets
1170	Fair value of the plan assets	Concept (Monetary)	As Of	Debit	ifrs-full:PlanAssetsAtFairValue
1171	Equities	Concept (Monetary)	As Of	Debit	ifrs-full:EquityInstrumentsAmountContributedToFairValueOfPlanAssets
1172	Pooled fund liability-driven investments	Concept (Monetary)	As Of	Debit	stn:PooledFundLiabilityDrivenInvestmentsAmountContributedToFairValueOfPlanAssets
1173	Property funds	Concept (Monetary)	As Of	Debit	ifrs-full:InvestmentFundsAmountContributedToFairValueOfPlanAssets
1174	1119 - Disclosure - Employee Defined Benefit Obligations - Summary of Principal Assumptions Used In Determining Pension Benefit Obligations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfPrincipalAssumptionsUsedInDeterminingPensionBenefitObligations
1175	Implied Table	Table	*	*	implied:Table
1176	Disclosure of defined benefit plans [abstract]	Abstract			ifrs-full:DisclosureOfDefinedBenefitPlansAbstract
1177	Disclosure of defined benefit plans [line items]	LineItems			ifrs-full:DisclosureOfDefinedBenefitPlansLineItems
1178	Discount rate	Concept (Percent)	As Of		ifrs-full:ActuarialAssumptionOfDiscountRates
1179	Rate of increase in salaries	Concept (Percent)	As Of		ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreases
1180	Rate of inflation, pre-retirement	Concept (Percent)	As Of		stn:ActuarialAssumptionOfExpectedRatesOfInflationPreRetirement
1181	Rate of increase in future pensions payment	Concept (Percent)	As Of		ifrs-full:ActuarialAssumptionOfExpectedRatesOfPensionIncreases
1182	Life expectancy at age 65 for current pensioners:	Abstract			stn:LifeExpectancyAtAgeSixtyFiveForCurrentPensionersAbstract
1183	Male	Concept (xbrli:durationItemType)	For Period		stn:LifeExpectancyAtAgeSixtyFiveForCurrentPensionersMale
1184	Female	Concept (xbrli:durationItemType)	For Period		stn:LifeExpectancyAtAgeSixtyFiveForCurrentPensionersFemale
1185	Life expectancy at age 65 for current members aged 40 or 45:	Abstract			stn:LifeExpectancyAtAgeSixtyFiveForCurrentMembersAgedFortyAbstract
1186	Male	Concept (xbrli:durationItemType)	For Period		stn:LifeExpectancyAtAgeSixtyFiveForCurrentMembersAgedFortyMale
1187	Female	Concept (xbrli:durationItemType)	For Period		stn:LifeExpectancyAtAgeSixtyFiveForCurrentMembersAgedFortyFemale
1188	1120 - Disclosure - Employee Defined Benefit Obligations - Summary of Quantitative Sensitivity Analyses Impact on Defined Benefit Obligation for Significant Assumptions (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfQuantitativeSensitivityAnalysesImpactOnDefinedBenefitObligationForSignificantAssumptions
1189	Disclosure of sensitivity analysis for actuarial assumptions [table]	Table	*	*	ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsTable
1190	Actuarial assumptions [axis]	Axis			ifrs-full:ActuarialAssumptionsAxis
1191	Actuarial assumptions [member]	Member			ifrs-full:ActuarialAssumptionsMember
1192	Change in discount rate by 0.25% [member]	Member			stn:ActuarialAssumptionOfDiscountRatesZeroPointTwoFivePercentMember
1193	Change in pre-retirement inflation rate by 0.25% [member]	Member			stn:ActuarialAssumptionOfExpectedRatesOfInflationPreRetirementZeroPointTwoFivePercentMember
1194	Change in salary growth by 0.25% [member]	Member			stn:ActuarialAssumptionOfExpectedRatesOfSalaryIncreasesZeroPointTwoFivePercentMember
1195	Change in pension increase assumption by 0.25% [member]	Member			stn:ActuarialAssumptionOfExpectedRatesOfPensionIncreasesZeroPointTwoFivePercentMember
1196	Increase of one year in the life expectancy [member]	Member			stn:ActuarialAssumptionsOfExpectedIncreaseOfOneYearInLifeExpectancyMember
1197	Disclosure of sensitivity analysis for actuarial assumptions [Line Items]	LineItems			ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
1198	Increase	Concept (Monetary)	As Of	Credit	ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleIncreaseInActuarialAssumption
1199	Decrease	Concept (Monetary)	As Of	Credit	ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleDecreaseInActuarialAssumption
1200	1121 - Disclosure - Employee Defined Benefit Obligations - Summary of Quantitative Sensitivity Analyses Impact on Defined Benefit Obligation for Significant Assumptions (Parenthetical) (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeDefinedBenefitObligationsSummaryOfQuantitativeSensitivityAnalysesImpactOnDefinedBenefitObligationForSignificantAssumptionsParenthetical
1201	Implied Table	Table	*	*	implied:Table
1202	Disclosure of sensitivity analysis for actuarial assumptions [abstract]	Abstract			ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsAbstract
1203	Percentage of increase	Concept (Percent)	As Of		ifrs-full:PercentageOfReasonablyPossibleIncreaseInActuarialAssumption
1204	Percentage of decrease	Concept (Percent)	As Of		ifrs-full:PercentageOfReasonablyPossibleDecreaseInActuarialAssumption
1205	1122 - Disclosure - Other Liabilities - Summary of Other Liabilities (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureOtherLiabilitiesSummaryOfOtherLiabilities
1206	Implied Table	Table	*	*	implied:Table
1207	Liabilities [abstract]	Abstract			ifrs-full:LiabilitiesAbstract
1208	Lease inducement benefits	Concept (Monetary)	As Of	Credit	stn:LeaseInducementBenefits
1209	Deferred share units payable	Concept (Monetary)	As Of	Credit	stn:DeferredShareUnitsPayable
1210	Other cash-settled share-based compensation	Concept (Monetary)	As Of	Credit	stn:OtherCashSettledSharebasedCompensation
1211	Liability for uncertain tax positions	Concept (Monetary)	As Of	Credit	stn:LiabilityForUncertainTaxPositions
1212	Other	Concept (Monetary)	As Of	Credit	stn:MiscellaneousOtherLiabilities
1213	Other liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:OtherLiabilities
1214	Other liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:OtherLiabilities
1215	Less current portion	Concept (Monetary)	As Of	Credit	ifrs-full:OtherCurrentLiabilities
1216	Long-term portion	Concept (Monetary)	As Of	Credit	ifrs-full:OtherNoncurrentLiabilities
1217	1123 - Disclosure - Commitments - Summary of Future Minimum Lease Payments Payable Under Noncancellable Operating Leases (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureCommitmentsSummaryOfFutureMinimumLeasePaymentsPayableUnderNoncancellableOperatingLeases
1218	Disclosure of maturity analysis of operating lease payments and purchase obligations [table]	Table	*	*	stn:DisclosureOfMaturityAnalysisOfOperatingLeasePaymentsAndPurchaseObligationsTable
1219	Maturity [axis]	Axis			ifrs-full:MaturityAxis
1220	Aggregated time bands [member]	Member			ifrs-full:AggregatedTimeBandsMember
1221	Within one year [member]	Member			ifrs-full:NotLaterThanOneYearMember
1222	2018 to 2022 [member]	Member			ifrs-full:LaterThanOneYearAndNotLaterThanFiveYearsMember
1223	More than five years [member]	Member			ifrs-full:LaterThanFiveYearsMember
1224	Disclosure of maturity analysis of operating lease payments and purchase obligations [line items]	LineItems			stn:DisclosureOfMaturityAnalysisOfOperatingLeasePaymentsAndPurchaseObligationsLineItems
1225	Future Minimum Lease Payments Payable	Concept (Monetary)	As Of	Credit	stn:MinimumLeasePaymentsPayableUnderNoncancellableOperatingLeaseAndPurchaseObligations
1226	Variable payments and non-lease elements	Concept (Monetary)	For Period	Debit	stn:VariableAndNonLeaseComponentUnderNoncancellableOperatingLease
1227	Purchase obligations	Concept (Monetary)	For Period	Debit	stn:PurchaseContractualObligation
1228	Total minimum lease payments	Concept (Monetary)	As Of	Credit	ifrs-full:MinimumLeasePaymentsPayableUnderNoncancellableOperatingLease
1229	1124 - Disclosure - Commitments - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureCommitmentsAdditionalInformation
1230	Implied Table	Table	*	*	implied:Table
1231	Commitments [abstract]	Abstract			stn:CommitmentsAbstract
1232	Premises rental expense	Concept (Monetary)	For Period	Debit	ifrs-full:RentalExpense
1233	Sublease rental income	Concept (Monetary)	For Period	Credit	ifrs-full:RentalIncome
1234	Future minimum sublease payments expected to be received under noncancellable sublease agreements	Concept (Monetary)	As Of	Debit	ifrs-full:ExpectedFutureMinimumSubleasePaymentsReceivableUnderNoncancellableSubleasesClassifiedAsOperatingLease
1235	1125 - Disclosure - Contingencies and Guarantees - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureContingenciesAndGuaranteesAdditionalInformation
1236	Disclosure of contingent liabilities [table]	Table	*	*	ifrs-full:DisclosureOfContingentLiabilitiesTable
1237	Classes of contingent liabilities [axis]	Axis			ifrs-full:ClassesOfContingentLiabilitiesAxis
1238	Contingent liabilities [member]	Member			ifrs-full:ContingentLiabilitiesMember
1239	Contingent liability for guarantees [member]	Member			ifrs-full:ContingentLiabilityForGuaranteesMember
1240	Disclosure of contingent liabilities [line items]	LineItems			ifrs-full:DisclosureOfContingentLiabilitiesLineItems
1241	Accrual of indemnifications or guarantees	Concept (Monetary)	As Of		ifrs-full:EstimatedFinancialEffectOfContingentAssets
1242	1126 - Disclosure - Share Capital - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalAdditionalInformation
1243	Implied Table	Table	*	*	implied:Table
1244	Disclosure of classes of share capital [abstract]	Abstract			ifrs-full:DisclosureOfClassesOfShareCapitalAbstract
1245	Description on par value of share	Concept (Text/String)	For Period		ifrs-full:ExplanationOfFactThatSharesHaveNoParValue
1246	Repurchase of common shares	Concept (Shares)	For Period		stn:SharesApprovedInNormalCourseIssuerBid
1247	Shares Repurchased for cancellation	Concept (Shares)	As Of		stn:SharesRepurchasedForCancellation
1248	Shares repurchased for cancellation	Concept (Monetary)	For Period	Credit	ifrs-full:CancellationOfTreasuryShares
1249	Reduction in share capital	Concept (Monetary)	For Period	Debit	ifrs-full:ReductionOfIssuedCapital
1250	Reduction in share capital and contributed surplus accounts	Concept (Monetary)	For Period	Debit	stn:ReductionOfShareCapitalAndContributedSurplus
1251	Charges to retained earnings	Concept (Monetary)	As Of	Credit	stn:ChargesToRetainedEarnings
1252	Share-based compensation expense	Concept (Monetary)	For Period	Debit	ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
1253	Expense related to fair value of options granted	Concept (Monetary)	For Period	Debit	stn:ExpenseRelatedToFairValueOfOptionsGranted
1254	Expense related to amortization of fair value of options granted	Concept (Monetary)	For Period	Debit	stn:ExpenseRelatedToAmortizationOfFairValueOfOptionsGranted
1255	Dividends declared included in trade and other payables	Concept (Monetary)	As Of	Credit	ifrs-full:DividendPayables
1256	1127 - Disclosure - Share Capital - Summary of Dividends Declared and Recorded in the Consolidated Financial Statements (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalSummaryOfDividendsDeclaredAndRecordedInTheConsolidatedFinancialStatements
1257	Disclosure of Dividends [table]	Table	*	*	stn:DisclosureOfDividendsTable
1258	Classes of ordinary shares [axis]	Axis			ifrs-full:ClassesOfOrdinarySharesAxis
1259	Ordinary Shares [Member]	Member			ifrs-full:OrdinarySharesMember
1260	Dividends per share one [member]	Member			stn:DividendsPerShareOneMember
1261	Dividends per share two [member]	Member			stn:DividendsPerShareTwoMember
1262	Dividends per share three [member]	Member			stn:DividendsPerShareThreeMember
1263	Dividends per share four [member]	Member			stn:DividendsPerShareFourMember
1264	Disclosure of Dividends [line items]	LineItems			stn:DisclosureOfDividendsLineItems
1265	Dividend per Share	Concept (Share)	For Period		ifrs-full:DividendsPaidOrdinarySharesPerShare
1266	Paid	Concept (Monetary)	For Period	Debit	ifrs-full:DividendsPaidOrdinaryShares
1267	Date Declared	Concept (Date)	For Period		stn:DividendsDeclaredDate
1268	Record Date	Concept (Date)	For Period		stn:DividendsRecordDate
1269	Payment Date	Concept (Date)	For Period		stn:DividendsPayableDate
1270	1128 - Disclosure - Share Capital - Share-based Payment Transactions - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalSharebasedPaymentTransactionsAdditionalInformation
1271	Disclosure of terms and conditions of share-based payment arrangement [table]	Table	*	*	ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
1272	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
1273	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
1274	Officers and employees [member]	Member			stn:OfficersAndEmployeesMember
1275	Vesting 1 [axis]	Axis			stn:Vesting1Axis
1276	Vesting 1 [domain]	Member			stn:Vesting1Domain
1277	Estimated historical data [member]	Member			stn:EstimatedHistoricalDataMember
1278	Types of share-based payment arrangements [axis]	Axis			ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
1279	Share-based payment arrangements [member]	Member			ifrs-full:SharebasedPaymentArrangementsMember
1280	Performance share units (PSUs) [member]	Member			stn:PerformanceShareUnitsMember
1281	Deferred share unit [member]	Member			stn:DeferredShareUnitMember
1282	Range [axis]	Axis			ifrs-full:RangeAxis
1283	Ranges [member]	Member			ifrs-full:RangesMember
1284	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
1285	Top of range [member]	Member			ifrs-full:TopOfRangeMember
1286	Disclosure of range of exercise prices of outstanding share options [line items]	LineItems			ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsLineItems
1287	Number of share subject to options, Granted	Concept (Decimal)	As Of		ifrs-full:NumberOfOutstandingShareOptions
1288	Share option price per share	Concept (Monetary)	As Of		ifrs-full:ExercisePriceOfOutstandingShareOptions
1289	Fair value of options granted	Concept (Text/String)	For Period		ifrs-full:DescriptionOfOptionPricingModelShareOptionsGranted
1290	Number of share subject to options, Granted	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
1291	Estimated fair value of options granted on the grant date	Concept (Monetary)	As Of	Credit	ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
1292	Expected hold period to exercise (years)	Concept (Decimal)	For Period		ifrs-full:DescriptionOfOptionLifeShareOptionsGranted
1293	Options remained unvested compensation cost	Concept (Monetary)	For Period	Debit	ifrs-full:ExpenseFromSharebasedPaymentTransactionsInWhichGoodsOrServicesReceivedDidNotQualifyForRecognitionAsAssets
1294	Options remained unvested weighted average period	Concept (Decimal)	As Of		stn:WeightedAverageRemainingContractualLifeOfOutstandingNonVestedShareOptions
1295	Number of units vest percentage	Concept (Percent)	For Period		stn:SharebasedPaymentArrangementVestingRightsPercentage
1296	Number of shares issued	Concept (Decimal)	For Period		ifrs-full:NumberOfInstrumentsOtherEquityInstrumentsGranted
1297	Number of equity instruments forfeited	Concept (Decimal)	For Period		ifrs-full:NumberOfOtherEquityInstrumentsForfeitedInSharebasedPaymentArrangement
1298	Number of shares outstanding	Concept (Decimal)	As Of		ifrs-full:NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
1299	Outstanding fair value	Concept (Monetary)	As Of	Credit	stn:FairValueOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
1300	Number of shares paid	Concept (Shares)	As Of		stn:NumberOfOtherEquityInstrumentsPaidInSharebasedPaymentArrangement
1301	Paid at fair value	Concept (Monetary)	As Of	Credit	stn:FairValueOfOtherEquityInstrumentsPaidInSharebasedPaymentArrangement
1302	1129 - Disclosure - Share Capital - Summary of Granted Share Options (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalSummaryOfGrantedShareOptions
1303	Disclosure of terms and conditions of share-based payment arrangement [table]	Table	*	*	ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
1304	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
1305	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
1306	Officers and employees [member]	Member			stn:OfficersAndEmployeesMember
1307	Disclosure of terms and conditions of share-based payment arrangement [line items]	LineItems			ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
1308	Share options, beginning of the year	Concept (Decimal)	As Of		ifrs-full:NumberOfOutstandingShareOptions
1309	Share options, Granted	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
1310	Share options, Exercised	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
1311	Share options, Forfeited	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsForfeitedInSharebasedPaymentArrangement
1312	Share options, end of the year	Concept (Decimal)	As Of		ifrs-full:NumberOfOutstandingShareOptions
1313	Weighted Average Exercise Price, Share option, beginning of the year	Concept (Monetary)	As Of		ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1314	Weighted Average Exercise Price, Share option, Granted	Concept (Monetary)	For Period		ifrs-full:WeightedAverageExercisePriceOfShareOptionsGrantedInSharebasedPaymentArrangement
1315	Weighted Average Exercise Price, Share option, Exercised	Concept (Monetary)	For Period		ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisedInSharebasedPaymentArrangement
1316	Weighted Average Exercise Price, Share option, Forfeited	Concept (Monetary)	For Period		ifrs-full:WeightedAverageExercisePriceOfShareOptionsForfeitedInSharebasedPaymentArrangement
1317	Weighted Average Exercise Price, Share option, end of the year	Concept (Monetary)	As Of		ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1318	1130 - Disclosure - Share Capital - Summary of Outstanding Share Options (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalSummaryOfOutstandingShareOptions
1319	Disclosure of number and weighted average remaining contractual life of outstanding share options [table]	Table	*	*	ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsTable
1320	Range [axis]	Axis			ifrs-full:RangeAxis
1321	Ranges [member]	Member			ifrs-full:RangesMember
1322	Bottom of range [member]	Member			ifrs-full:BottomOfRangeMember
1323	Top of range [member]	Member			ifrs-full:TopOfRangeMember
1324	Ranges of exercise prices for outstanding share options [axis]	Axis			ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsAxis
1325	Range one [Member]	Member			ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsMember
1326	Range one [member]	Member			stn:RangesOfExercisePricesForOutstandingShareOptionsOneMember
1327	Range two [member]	Member			stn:RangesOfExercisePricesForOutstandingShareOptionsTwoMember
1328	Range three [member]	Member			stn:RangesOfExercisePricesForOutstandingShareOptionsThreeMember
1329	Range four [member]	Member			stn:RangesOfExercisePricesForOutstandingShareOptionsFourMember
1330	Disclosure of number and weighted average remaining contractual life of outstanding share options [line items]	LineItems			ifrs-full:DisclosureOfNumberAndWeightedAverageRemainingContractualLifeOfOutstandingShareOptionsLineItems
1331	Range of Exercise Prices	Concept (Monetary)	As Of		ifrs-full:ExercisePriceOfOutstandingShareOptions
1332	Options Outstanding	Concept (Decimal)	As Of		ifrs-full:NumberOfOutstandingShareOptions
1333	Weighted Average Remaining Contractual Life in Years, Options Outstanding	Concept (Decimal)	As Of		ifrs-full:WeightedAverageRemainingContractualLifeOfOutstandingShareOptions
1334	Weighted Average Exercise Price, Options Outstanding	Concept (Monetary)	As Of		ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1335	Shares Exercisable	Concept (Decimal)	As Of		ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
1336	Weighted Average Remaining Contractual Life in Years, Options Exercisable	Concept (Decimal)	For Period		stn:WeightedAverageRemainingContractualLifeOfExercisableShareOptions
1337	Weighted Average Exercise Price, Options Exercisable	Concept (Monetary)	As Of		ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisableInSharebasedPaymentArrangement
1338	1131 - Disclosure - Share Capital - Summary of Weighted Average Assumptions (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalSummaryOfWeightedAverageAssumptions
1339	Implied Table	Table	*	*	implied:Table
1340	Disclosure of terms and conditions of share-based payment arrangement [abstract]	Abstract			ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementAbstract
1341	Volatility in the price of the Company's shares	Concept (Percent)	For Period		ifrs-full:DescriptionOfExpectedVolatilityShareOptionsGranted
1342	Risk-free interest rate	Concept (Percent)	For Period		ifrs-full:DescriptionOfRiskFreeInterestRateShareOptionsGranted
1343	Expected hold period to exercise (years)	Concept (Decimal)	For Period		ifrs-full:DescriptionOfOptionLifeShareOptionsGranted
1344	Dividend yield	Concept (Percent)	For Period		ifrs-full:ExpectedDividendAsPercentageShareOptionsGranted
1345	Exercise price	Concept (Monetary)	For Period		ifrs-full:ExercisePriceShareOptionsGranted
1346	1132 - Disclosure - Share Capital - Summary of Non-Vested Options (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureShareCapitalSummaryOfNonVestedOptions
1347	Disclosure of terms and conditions of share-based payment arrangement [table]	Table	*	*	ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
1348	Types of share-based payment arrangements [axis]	Axis			ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
1349	Share-based payment arrangements [member]	Member			ifrs-full:SharebasedPaymentArrangementsMember
1350	Non-vested options [member]	Member			stn:NonvestedOptionsMember
1351	Disclosure of terms and conditions of share-based payment arrangement [line items]	LineItems			ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
1352	Share options, beginning of the year	Concept (Decimal)	As Of		ifrs-full:NumberOfOutstandingShareOptions
1353	Number of share subject to options, Granted	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsGrantedInSharebasedPaymentArrangement
1354	Number of share subject to options, Vested	Concept (Decimal)	As Of		stn:NumberOfShareOptionsVestedInSharebasedPaymentArrangement
1355	Number of share subject to options, Forfeited	Concept (Decimal)	For Period		ifrs-full:NumberOfShareOptionsForfeitedInSharebasedPaymentArrangement
1356	Share options, end of the year	Concept (Decimal)	As Of		ifrs-full:NumberOfOutstandingShareOptions
1357	Weighted average grant date fair value, Granted	Concept (Monetary)	As Of	Credit	ifrs-full:WeightedAverageFairValueAtMeasurementDateShareOptionsGranted
1358	Weighted average grant date fair value, Vested	Concept (Monetary)	For Period	Credit	stn:WeightedAverageFairValueAtMeasurementDateShareOptionsVested
1359	Weighted average grant date fair value, Forfeited	Concept (Monetary)	For Period	Credit	stn:WeightedAverageFairValueAtMeasurementDateShareOptionsForfeited
1360	Weighted average grant date fair value, Non-vested share options	Concept (Monetary)	For Period		stn:WeightedAverageFairValueAtReportingDateShareOptionsNonVested
1361	1133 - Disclosure - Fair Value Measurements - Summary of Fair Value Hierarchy for Assets (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfFairValueHierarchyForAssets
1362	Disclosure of fair value measurement of assets [table]	Table	*	*	ifrs-full:DisclosureOfFairValueMeasurementOfAssetsTable
1363	Measurement [axis]	Axis			ifrs-full:MeasurementAxis
1364	Aggregated measurement [member]	Member			ifrs-full:AggregatedMeasurementMember
1365	Recurring fair value measurement [member]	Member			ifrs-full:RecurringFairValueMeasurementMember
1366	Levels of fair value hierarchy [axis]	Axis			ifrs-full:LevelsOfFairValueHierarchyAxis
1367	All levels of fair value hierarchy [member]	Member			ifrs-full:AllLevelsOfFairValueHierarchyMember
1368	Significant other observable inputs [member]	Member			ifrs-full:Level2OfFairValueHierarchyMember
1369	Classes of assets [axis]	Axis			ifrs-full:ClassesOfAssetsAxis
1370	Assets [member]	Member			ifrs-full:ClassesOfAssetsMember
1371	Investments held for self-insured liabilities [member]	Member			stn:InvestmentsHeldForSelfInsuredLiabilitiesMember
1372	Disclosure of fair value measurement of assets [line items]	LineItems			ifrs-full:DisclosureOfFairValueMeasurementOfAssetsLineItems
1373	Other financial assets	Concept (Monetary)	As Of	Debit	ifrs-full:OtherFinancialAssets
1374	1134 - Disclosure - Fair Value Measurements - Summary of Fair Value Hierarchy for Liabilities (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfFairValueHierarchyForLiabilities
1375	Disclosure of fair value measurement of liabilities [table]	Table	*	*	ifrs-full:DisclosureOfFairValueMeasurementOfLiabilitiesTable
1376	Measurement [axis]	Axis			ifrs-full:MeasurementAxis
1377	Aggregated measurement [member]	Member			ifrs-full:AggregatedMeasurementMember
1378	Not measured at fair value in statement of financial position but for which fair value is disclosed [Member]	Member			ifrs-full:NotMeasuredAtFairValueInStatementOfFinancialPositionButForWhichFairValueIsDisclosedMember
1379	Levels of fair value hierarchy [axis]	Axis			ifrs-full:LevelsOfFairValueHierarchyAxis
1380	All levels of fair value hierarchy [member]	Member			ifrs-full:AllLevelsOfFairValueHierarchyMember
1381	Significant other observable inputs [member]	Member			ifrs-full:Level2OfFairValueHierarchyMember
1382	Disclosure of fair value measurement of liabilities [line items]	LineItems			ifrs-full:DisclosureOfFairValueMeasurementOfLiabilitiesLineItems
1383	Notes payable	Concept (Monetary)	As Of	Credit	stn:NotesPayable1
1384	1135 - Disclosure - Financial Instruments - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformation
1385	Disclosure of detailed information about financial instruments [table]	Table	*	*	ifrs-full:DisclosureOfFinancialInstrumentsTable
1386	Borrowings by name [axis]	Axis			ifrs-full:BorrowingsByNameAxis
1387	Borrowings by name [member]	Member			ifrs-full:BorrowingsByNameMember
1388	Revolving credit facilities [member]	Member			stn:RevolvingCreditFacility1Member
1389	Range [axis]	Axis			ifrs-full:RangeAxis
1390	Ranges [member]	Member			ifrs-full:RangesMember
1391	Top of range [member]	Member			ifrs-full:TopOfRangeMember
1392	Types of risks [axis]	Axis			ifrs-full:TypesOfRisksAxis
1393	Risks [member]	Member			ifrs-full:TypesOfRisksMember
1394	0.5% Increase in interest rates [member]	Member			stn:ZeroPointFivePercentageIncreaseInInterestRatesMember
1395	0.5% Decrease in interest rates [member]	Member			stn:ZeroPointFivePercentageDecreaseInInterestRatesMember
1396	1.0% Increase in equity price risk [member]	Member			stn:OnePointZeroPercentageIncreaseInEquityPriceRiskMember
1397	1.0% Decrease in equity Price risk [member]	Member			stn:OnePointZeroPercentageDecreaseInEquityPriceRiskMember
1398	Classes of financial instruments [axis]	Axis			ifrs-full:ClassesOfFinancialInstrumentsAxis
1399	Financial instruments, class [member]	Member			ifrs-full:ClassesOfFinancialInstrumentsMember
1400	Trade and unbilled receivables [member]	Member			stn:TradeAndUnbilledReceivablesMember
1401	Contract assets and holdbacks [member]	Member			stn:ContractAssetsAndHoldbacksMember
1402	Disclosure of nature and extent of risks arising from financial instruments [line items]	LineItems			ifrs-full:DisclosureOfNatureAndExtentOfRisksArisingFromFinancialInstrumentsLineItems
1403	Maximum amount of credit risk exposure	Concept (Monetary)	As Of		ifrs-full:MaximumExposureToCreditRisk
1404	Number of target days of revenue in trade receivables	Concept (xbrli:durationItemType)	For Period		stn:PeriodOfRevenueInTradeReceivables
1405	Write off of trade receivables	Concept (Monetary)	For Period	Debit	stn:WriteOffOfTradeReceivables
1406	Trade and other receivables	Concept (Monetary)	As Of	Credit	ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1407	Amount of revolving credit facility	Concept (Monetary)	As Of	Credit	stn:LineOfCreditFacilityMaximumBorrowingsCapacity
1408	Unused capacity amount	Concept (Monetary)	As Of	Credit	stn:LineOfCreditFacilityRemainingBorrowingCapacity1
1409	Net debt to EBITDA ratio	Concept (Pure)	For Period		stn:NetDebtToEBITDARatioTarget
1410	Equity price impact on comprehensive income	Concept (Monetary)	For Period	Debit	stn:NetIncomeDecrease
1411	Equity price impact on comprehensive income	Concept (Monetary)	For Period	Credit	stn:NetIncomeIncrease
1412	1136 - Disclosure - Financial Instruments - Summary of Loss Allowance Provision (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfLossAllowanceProvision
1413	Disclosure of provision matrix [table]	Table	*	*	ifrs-full:DisclosureOfProvisionMatrixTable
1414	Past due status [axis]	Axis			ifrs-full:PastDueStatusAxis
1415	Past due status [member]	Member			ifrs-full:PastDueStatusMember
1416	Current [member]	Member			ifrs-full:CurrentMember
1417	Later than one month and not later than two months [member]	Member			ifrs-full:LaterThanOneMonthAndNotLaterThanTwoMonthsMember
1418	Later than two months and not later than three months [member]	Member			ifrs-full:LaterThanTwoMonthsAndNotLaterThanThreeMonthsMember
1419	Later than three months and not later than four months [member]	Member			ifrs-full:LaterThanThreeMonthsAndNotLaterThanFourMonthsMember
1420	Later than four months [member]	Member			ifrs-full:LaterThanFourMonthsMember
1421	Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis]	Axis			ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
1422	Carrying amount [member]	Member			ifrs-full:CarryingAmountMember
1423	Gross carrying amount [member]	Member			ifrs-full:GrossCarryingAmountMember
1424	Accumulated impairment [member]	Member			ifrs-full:AccumulatedImpairmentMember
1425	Disclosure of provision matrix [line items]	LineItems			ifrs-full:DisclosureOfProvisionMatrixLineItems
1426	Expected loss rate	Concept (Percent)	As Of		ifrs-full:ExpectedCreditLossRate
1427	Gross carrying amount	Concept (Monetary)	As Of	Debit	ifrs-full:FinancialAssets
1428	Loss allowance provision, end of the year	Concept (Monetary)	As Of	Credit	ifrs-full:AllowanceAccountForCreditLossesOfFinancialAssets
1429	1137 - Disclosure - Financial Instruments - Summary of Timing of Undiscounted Cash Outflows Relating to Financial Liabilities (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfTimingOfUndiscountedCashOutflowsRelatingToFinancialLiabilities
1430	Disclosure of maturity analysis for derivative financial liabilities [table]	Table	*	*	ifrs-full:DisclosureOfMaturityAnalysisForDerivativeFinancialLiabilitiesTable
1431	Maturity [axis]	Axis			ifrs-full:MaturityAxis
1432	Aggregated time bands [member]	Member			ifrs-full:AggregatedTimeBandsMember
1433	Within one year [member]	Member			ifrs-full:NotLaterThanOneYearMember
1434	Later than one year and not later than three years [member]	Member			ifrs-full:LaterThanOneYearAndNotLaterThanThreeYearsMember
1435	After 3 years [member]	Member			ifrs-full:LaterThanThreeYearsMember
1436	Disclosure of maturity analysis for non-derivative financial liabilities [line items]	LineItems			ifrs-full:DisclosureOfMaturityAnalysisForNonderivativeFinancialLiabilitiesLineItems
1437	Trade and other payables	Concept (Monetary)	As Of	Credit	ifrs-full:TradeAndOtherPayablesUndiscountedCashFlows
1438	Long-term debt	Concept (Monetary)	As Of	Credit	stn:LongTermDebtUndiscountedCashFlows
1439	Other financial liabilities	Concept (Monetary)	As Of	Credit	stn:OtherFinancialLiabilitiesUndiscountedCashFlows
1440	Total contractual obligations	Concept (Monetary)	As Of	Credit	ifrs-full:NonderivativeFinancialLiabilitiesUndiscountedCashFlows
1441	1138 - Disclosure - Capital Management - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureCapitalManagementAdditionalInformation
1442	Implied Table	Table	*	*	implied:Table
1443	Disclosure of capital management [abstract]	Abstract			stn:DisclosureOfCapitalManagementAbstract
1444	Net debt ratio	Concept (Pure)	For Period		stn:NetDebtToEBITDARatio
1445	1139 - Disclosure - Income Taxes - Summary of Effective Income Tax for Continuing Operations From Statutory Canadian Tax Rates (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesSummaryOfEffectiveIncomeTaxForContinuingOperationsFromStatutoryCanadianTaxRates
1446	Implied Table	Table	*	*	implied:Table
1447	Reconciliation of average effective tax rate and applicable tax rate [abstract]	Abstract			ifrs-full:ReconciliationOfAverageEffectiveTaxRateAndApplicableTaxRateAbstract
1448	Income tax expense at statutory Canadian rates	Concept (Percent)	For Period		ifrs-full:ApplicableTaxRate
1449	Increase (decrease) resulting from:	Abstract			stn:IncreaseDecreaseInTaxRateAbstract
1450	Transition tax related to US tax reform	Concept (Percent)	For Period		stn:TaxRateEffectOfTransitionTaxRelatedToTaxReform
1451	Rate differential on foreign income	Concept (Percent)	For Period		ifrs-full:TaxRateEffectOfForeignTaxRates
1452	Research and development and other tax credits	Concept (Percent)	For Period		stn:TaxRateEffectOfResearchAndDevelopmentAndOtherTaxCredits
1453	Unrecognized tax losses and temporary differences	Concept (Percent)	For Period		ifrs-full:TaxRateEffectOfTaxLosses
1454	Adjustments in respect of prior years and other	Concept (Percent)	For Period		stn:TaxRateEffectOfAdjustmentsForCurrentTaxOfPriorPeriodsAndOther
1455	Non-deductible expenses and non-taxable income	Concept (Percent)	For Period		stn:TaxRateEffectOfNonDeductibleExpenseAndNonTaxableIncome
1456	Reorganization of corporate structure	Concept (Percent)	For Period		stn:TaxRateEffectOfReorganizationOfCorporateStructure
1457	Disposition of a subsidiary	Concept (Percent)	For Period		stn:TaxRateEffectOfDispositionOfSubsidiary
1458	Statutory rate change on deferred tax balances	Concept (Percent)	For Period		ifrs-full:TaxRateEffectFromChangeInTaxRate
1459	Average effective tax rate	Concept (Percent)	For Period		ifrs-full:AverageEffectiveTaxRate
1460	1140 - Disclosure - Income Taxes - Summary of Major Components of Current Income Tax Expense from Continuing Operations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesSummaryOfMajorComponentsOfCurrentIncomeTaxExpenseFromContinuingOperations
1461	Implied Table	Table	*	*	implied:Table
1462	Major components of tax expense (income) [abstract]	Abstract			ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
1463	Ongoing operations	Concept (Monetary)	For Period	Debit	stn:IncomeTaxExpenseContinuingOperationsCurrent
1464	Transition tax related to US tax reform	Concept (Monetary)	For Period	Debit	stn:TaxExpenseRelatingToTransitionTaxRelatedToTaxReform
1465	Disposition of subsidiary	Concept (Monetary)	For Period	Debit	stn:TaxExpenseRelatingToDispositionOfSubsidiary
1466	Reorganization of corporate structure	Concept (Monetary)	For Period	Debit	stn:TaxExpenseRelatingToReorganizationOfCorporateStructure
1467	Total current income tax expense	Concept (Monetary)	For Period	Debit	ifrs-full:CurrentTaxExpenseIncome
1468	1141 - Disclosure - Income Taxes - Summary of Major Components of Deferred Income Tax (Recovery) Expense from Continuing Operations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesSummaryOfMajorComponentsOfDeferredIncomeTaxRecoveryExpenseFromContinuingOperations
1469	Implied Table	Table	*	*	implied:Table
1470	Major components of tax expense (income) [abstract]	Abstract			ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
1471	Unrecognized tax losses and temporary differences	Concept (Monetary)	For Period	Credit	ifrs-full:TaxBenefitArisingFromPreviouslyUnrecognisedTaxLossTaxCreditOrTemporaryDifferenceOfPriorPeriodUsedToReduceCurrentTaxExpense
1472	Origination and reversal of timing differences	Concept (Monetary)	For Period	Debit	ifrs-full:DeferredTaxExpenseIncomeRelatingToOriginationAndReversalOfTemporaryDifferences
1473	Recovery arising from previously unrecognized tax assets	Concept (Monetary)	For Period	Credit	ifrs-full:TaxBenefitArisingFromPreviouslyUnrecognisedTaxLossTaxCreditOrTemporaryDifferenceOfPriorPeriodUsedToReduceDeferredTaxExpense
1474	Change of tax rates	Concept (Monetary)	For Period	Debit	ifrs-full:DeferredTaxExpenseIncomeRelatingToTaxRateChangesOrImpositionOfNewTaxes
1475	Revaluation due to US tax reform	Concept (Monetary)	For Period	Debit	stn:DeferredTaxExpenseIncomeRelatingToTransitionTaxRelatedToTaxReform
1476	Disposition of a subsidiary	Concept (Monetary)	For Period	Debit	stn:DeferredTaxExpenseIncomeRelatingToDispositionOfSubsidiary
1477	Total deferred income tax expense (recovery)	Concept (Monetary)	For Period	Debit	ifrs-full:DeferredTaxExpenseIncome
1478	1142 - Disclosure - Income Taxes - Schedule of Significant Components of the Company's Net Deferred Income Tax Assets (Liabilities) (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfSignificantComponentsOfTheCompanysNetDeferredIncomeTaxAssetsLiabilities
1479	Disclosure of deferred income taxes [table]	Table	*	*	stn:DisclosureOfDeferredIncomeTaxesTable
1480	Temporary difference, unused tax losses and unused tax credits [axis]	Axis			ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
1481	Temporary difference, unused tax losses and unused tax credits [member]	Member			ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
1482	Intangible asset [member]	Member			stn:IntangibleAssetMember
1483	Property, plant and equipment [member]	Member			ifrs-full:PropertyPlantAndEquipmentMember
1484	Deferred tax arising in business acquisition [member]	Member			stn:DeferredTaxArisingInBusinessAcquisitionMember
1485	Non-capital and capital tax losses [member]	Member			ifrs-full:TemporaryDifferenceMember
1486	Loss and tax credit carryforwards [member]	Member			stn:UnusedTaxCreditsAndTaxLossesMember
1487	Deferred tax defined benefit obligation [member]	Member			stn:DeferredTaxDefinedBenefitObligationMember
1488	Other temporary differences [member]	Member			ifrs-full:OtherTemporaryDifferencesMember
1489	Disclosure of deferred income taxes [line items]	LineItems			stn:DisclosureOfDeferredIncomeTaxesLineItems
1490	Deferred income tax assets (liabilities)	Abstract			ifrs-full:NetDeferredTaxAssetsAndLiabilitiesAbstract
1491	Deferred tax liabilities	Concept (Monetary)	As Of	Credit	ifrs-full:NetDeferredTaxLiabilities
1492	Deferred income tax assets	Concept (Monetary)	As Of	Debit	ifrs-full:NetDeferredTaxAssets
1493	Deferred income tax assets (liabilities)	Concept (Monetary)	As Of	Credit	ifrs-full:DeferredTaxLiabilityAsset
1494	1143 - Disclosure - Income Taxes - Schedule of Reconciliation of Net Deferred Tax Assets (Liabilities) (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfNetDeferredTaxAssetsLiabilities
1495	Implied Table	Table	*	*	implied:Table
1496	Reconciliation of changes in deferred tax liability (asset) [abstract]	Abstract			ifrs-full:ReconciliationOfChangesInDeferredTaxLiabilityAssetAbstract
1497	Beginning balance	Concept (Monetary)	As Of	Credit	ifrs-full:DeferredTaxLiabilityAsset
1498	Discontinued operations	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughLossOfControlOfSubsidiaryDeferredTaxLiabilityAsset
1499	Impact of foreign exchange	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesDeferredTaxLiabilityAsset
1500	Adoption of IFRS 15 and IFRS 9	Concept (Monetary)	For Period	Credit	stn:IncreaseDecreaseThroughAdoptionOfIfrs15AndIfrs9DeferredTaxLiabilityAsset
1501	Tax effect on other comprehensive income	Concept (Monetary)	For Period		ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncome
1502	Tax recovery during the year recognized in net income	Concept (Monetary)	For Period		ifrs-full:DeferredTaxExpenseIncomeRecognisedInProfitOrLoss
1503	Deferred taxes acquired through business combinations	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughBusinessCombinationsDeferredTaxLiabilityAsset
1504	Other	Concept (Monetary)	For Period	Credit	stn:IncreaseDecreaseThroughOtherDeferredTaxLiabilityAsset
1505	Ending balance	Concept (Monetary)	As Of	Credit	ifrs-full:DeferredTaxLiabilityAsset
1506	1144 - Disclosure - Income Taxes - Schedule of Loss Carryforwards (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfLossCarryforwards
1507	Disclosure of temporary difference, unused tax losses and unused tax credits [table]	Table	*	*	ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
1508	Temporary difference, unused tax losses and unused tax credits [axis]	Axis			ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
1509	Temporary difference, unused tax losses and unused tax credits [member]	Member			ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
1510	Non-capital tax losses [member]	Member			stn:NonCapitalTaxLossesMember
1511	Capital tax loss [member]	Member			stn:CapitalTaxLossMember
1512	Non-capital and capital tax losses [member]	Member			ifrs-full:TemporaryDifferenceMember
1513	Maturity [axis]	Axis			ifrs-full:MaturityAxis
1514	Aggregated time bands [member]	Member			ifrs-full:AggregatedTimeBandsMember
1515	Expiry 2019 To 2038 [member]	Member			stn:Expiry2019To2038Member
1516	Never expire [member]	Member			stn:NeverExpireMember
1517	Disclosure of temporary difference, unused tax losses and unused tax credits [line items]	LineItems			ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
1518	Deductible temporary differences	Concept (Monetary)	As Of		ifrs-full:DeductibleTemporaryDifferencesForWhichNoDeferredTaxAssetIsRecognised
1519	Capital tax losses	Concept (Monetary)	As Of		ifrs-full:UnusedTaxLossesForWhichNoDeferredTaxAssetRecognised
1520	1145 - Disclosure - Income Taxes - Additional Informations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureIncomeTaxesAdditionalInformations
1521	Disclosure of Income Tax [table]	Table	*	*	stn:DisclosureOfIncomeTaxTable
1522	Geographical areas [axis]	Axis			ifrs-full:GeographicalAreasAxis
1523	Geographical areas [member]	Member			ifrs-full:GeographicalAreasMember
1524	United States [member]	Member			country:US
1525	Disclosure of income tax [line items]	LineItems			stn:DisclosureOfIncomeTaxLineItems
1526	Transition tax related to US tax reform	Concept (Monetary)	For Period	Debit	stn:TaxExpenseRelatingToTransitionTaxRelatedToTaxReform
1527	Revaluation due to US tax reform	Concept (Monetary)	For Period	Debit	stn:DeferredTaxExpenseIncomeRelatingToTransitionTaxRelatedToTaxReform
1528	Federal tax rate	Concept (Percent)	For Period		ifrs-full:ApplicableTaxRate
1529	1146 - Disclosure - Net Interest Expense and Other Net Finance Expense - Schedule of Interest Expense (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureNetInterestExpenseAndOtherNetFinanceExpenseScheduleOfInterestExpense
1530	Disclosure Of Net Interest Expense Income [table]	Table	*	*	stn:DisclosureOfNetInterestExpenseIncomeTable
1531	Classes of financial instruments [axis]	Axis			ifrs-full:ClassesOfFinancialInstrumentsAxis
1532	Financial instruments, class [member]	Member			ifrs-full:ClassesOfFinancialInstrumentsMember
1533	Notes payable [member]	Member			stn:NotesPayableMember
1534	Revolving credit facilities [member]	Member			stn:RevolvingCreditFacility1Member
1535	Disclosure of net interest expense income [line items]	LineItems			stn:DisclosureOfNetInterestExpenseIncomeLineItems
1536	Interest Expense	Concept (Monetary)	For Period	Debit	ifrs-full:InterestExpenseOnBorrowings
1537	Interest on finance leases	Concept (Monetary)	For Period	Debit	ifrs-full:InterestExpenseOnFinanceLeases
1538	Other	Concept (Monetary)	For Period	Debit	stn:InterestExpenseOnOther
1539	Total interest expense	Concept (Monetary)	For Period	Debit	ifrs-full:InterestExpense
1540	Interest income on FVOCI investment debt securities	Concept (Monetary)	For Period	Credit	ifrs-full:InterestRevenueForFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncome
1541	Other	Concept (Monetary)	For Period	Credit	ifrs-full:InterestIncomeOnOtherFinancialAssets
1542	Total interest income	Concept (Monetary)	For Period	Credit	ifrs-full:RevenueFromInterest
1543	Net interest expense	Concept (Monetary)	For Period	Credit	ifrs-full:InterestRevenueExpense
1544	1147 - Disclosure - Net Interest Expense and Other Net Finance Expense - Schedule of Other Net Finance Expense (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureNetInterestExpenseAndOtherNetFinanceExpenseScheduleOfOtherNetFinanceExpense
1545	Implied Table	Table	*	*	implied:Table
1546	Disclosure of other net finance expense [abstract]	Abstract			stn:DisclosureOfOtherNetFinanceExpenseAbstract
1547	Realized loss on sale of FVOCI investment debt securities	Concept (Monetary)	For Period	Debit	stn:LossOnSaleOfFinancialAssetsAtFairValueThroughOtherComprehensiveIncome
1548	Amortization on FVOCI investment debt securities	Concept (Monetary)	For Period	Debit	stn:AmortizationOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncome
1549	Bank charges	Concept (Monetary)	For Period	Debit	ifrs-full:BankAndSimilarCharges
1550	Total other finance expense	Concept (Monetary)	For Period	Debit	stn:OtherFinanceExpense
1551	Realized gain on sale of FVOCI investment debt securities	Concept (Monetary)	For Period	Credit	stn:OtherFinanceIncomeOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncome
1552	Derecognition of notes payable	Concept (Monetary)	For Period	Credit	stn:DerecognitionOfNotesPayable
1553	Other net finance expense	Concept (Monetary)	For Period	Debit	ifrs-full:OtherFinanceCost
1554	1148 - Disclosure - Revenue - Summary of Information about Receivables, Contract Assets, and Deferred Revenue (Contract Liabilities) from Contracts with Customers (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRevenueSummaryOfInformationAboutReceivablesContractAssetsAndDeferredRevenueContractLiabilitiesFromContractsWithCustomers
1555	Implied Table	Table	*	*	implied:Table
1556	Disclosure of disaggregation of revenue from contracts with customers [abstract]	Abstract			ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersAbstract
1557	Receivables	Abstract			ifrs-full:ReceivablesFromContractsWithCustomersAbstract
1558	Trade receivables and holdbacks	Concept (Monetary)	As Of	Debit	stn:TradeReceivableHoldbacks
1559	Unbilled receivables	Concept (Monetary)	As Of	Debit	stn:UnbilledReceivables
1560	Contract assets	Concept (Monetary)	As Of	Debit	ifrs-full:CurrentContractAssets
1561	Deferred revenue	Concept (Monetary)	As Of	Credit	ifrs-full:CurrentContractLiabilities
1562	Total Consulting Services	Concept (Monetary)	As Of	Debit	ifrs-full:ReceivablesFromContractsWithCustomers
1563	1149 - Disclosure - Revenue - Significant Increases (Decreases) in Contract Assets and Deferred Revenue (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRevenueSignificantIncreasesDecreasesInContractAssetsAndDeferredRevenue
1564	Disclosure of disaggregation of revenue from contracts with customers [table]	Table	*	*	ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersTable
1565	Contract Assets Liabilities [axis]	Axis			stn:ContractAssetsLiabilitiesAxis
1566	Contract Assets Liabilities [member]	Member			stn:ContractAssetsLiabilitiesMember
1567	Current Contract Assets [member]	Member			stn:CurrentContractAssetsMember
1568	Current Contract Liabilities [member]	Member			stn:CurrentContractLiabilitiesMember
1569	Disclosure of disaggregation of revenue from contracts with customers [line items]	LineItems			ifrs-full:DisclosureOfDisaggregationOfRevenueFromContractsWithCustomersLineItems
1570	Acquisitions	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseThroughBusinessCombinationsContractLiabilities
1571	Acquisitions	Concept (Monetary)	For Period	Debit	ifrs-full:IncreaseThroughBusinessCombinationsContractAssets
1572	Discontinued operations and disposition of subsidiaries	Concept (Monetary)	For Period	Debit	stn:DecreaseThroughDispositionsContractAssets
1573	Discontinued operations and disposition of subsidiaries	Concept (Monetary)	For Period	Debit	stn:DecreaseThroughDisposalFinancialLiabilities
1574	1150 - Disclosure - Revenue - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRevenueAdditionalInformation
1575	Implied Table	Table	*	*	implied:Table
1576	Disclosure of performance obligations [abstract]	Abstract			ifrs-full:DisclosureOfPerformanceObligationsAbstract
1577	Deferred revenue	Concept (Monetary)	For Period	Credit	ifrs-full:RevenueThatWasIncludedInContractLiabilityBalanceAtBeginningOfPeriod
1578	Explanation of how timing of satisfaction of performance obligations relates to typical timing of payment	Concept (Text/String)	For Period		ifrs-full:ExplanationOfHowTimingOfSatisfactionOfPerformanceObligationsRelatesToTypicalTimingOfPayment
1579	Revenue from performance obligations unsatisfied (or partially unsatisfied)	Concept (Monetary)	As Of	Credit	ifrs-full:TransactionPriceAllocatedToRemainingPerformanceObligations
1580	Expected revenue recognition as contracts	Concept (Percent)	For Period		stn:PercentageOfEntityWhichExpectsToRecogniseTransactionPriceAllocatedToRemainingPerformanceObligationsAsRevenue
1581	Explanation of expected revenue recognition as contracts	Concept (Text/String)	For Period		ifrs-full:ExplanationOfWhenEntityExpectsToRecogniseTransactionPriceAllocatedToRemainingPerformanceObligationsAsRevenue
1582	1151 - Disclosure - Employee Costs from Continuing Operations - Schedule of Employee Benefits Cost (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeCostsFromContinuingOperationsScheduleOfEmployeeBenefitsCost
1583	Implied Table	Table	*	*	implied:Table
1584	Disclosure of employee costs [abstract]	Abstract			stn:DisclosureOfEmployeeCostsAbstract
1585	Wages, salaries, and benefits	Concept (Monetary)	For Period	Debit	ifrs-full:ShorttermEmployeeBenefitsExpense
1586	Pension costs	Concept (Monetary)	For Period	Debit	stn:EmployeePensionCosts
1587	Share-based compensation	Concept (Monetary)	For Period	Debit	ifrs-full:ExpenseFromSharebasedPaymentTransactionsWithEmployees
1588	Total employee costs	Concept (Monetary)	For Period	Debit	ifrs-full:EmployeeBenefitsExpense
1589	Direct labor	Concept (Monetary)	For Period	Debit	stn:DirectLaborCosts
1590	Indirect labor	Concept (Monetary)	For Period	Debit	stn:IndirectLaborCosts
1591	Total employee costs	Concept (Monetary)	For Period	Debit	ifrs-full:EmployeeBenefitsExpense
1592	1152 - Disclosure - Employee Costs from Continuing Operations - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEmployeeCostsFromContinuingOperationsAdditionalInformation
1593	Disclosure Of Employee Cost [table]	Table	*	*	stn:DisclosureOfEmployeeCostTable
1594	Defined benefit plans [axis]	Axis			ifrs-full:DefinedBenefitPlansAxis
1595	Defined benefit plans [member]	Member			ifrs-full:DefinedBenefitPlansMember
1596	Defined contribution plans [member]	Member			stn:DefinedContributionPlansMember
1597	Disclosure of employee cost [line items]	LineItems			stn:DisclosureOfEmployeeCostLineItems
1598	Pension cost	Concept (Monetary)	For Period	Debit	ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
1599	1153 - Disclosure - Other Expense (Income) - Schedule of Other Expense (Income) (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureOtherExpenseIncomeScheduleOfOtherExpenseIncome
1600	Implied Table	Table	*	*	implied:Table
1601	Analysis of income and expense [abstract]	Abstract			ifrs-full:AnalysisOfIncomeAndExpenseAbstract
1602	Loss on sale of property and equipment	Concept (Monetary)	For Period	Credit	ifrs-full:GainsLossesOnDisposalsOfPropertyPlantAndEquipment
1603	Unrealized loss on equity securities	Concept (Monetary)	For Period	Credit	stn:UnrealizedGainsLossesOnFinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
1604	Net realized gain on equity securities	Concept (Monetary)	For Period	Credit	stn:RealizedGainsLossesOnFinancialAssetsAtFairValueThroughProfitOrLossMandatorilyMeasuredAtFairValue
1605	Other	Concept (Monetary)	For Period	Credit	stn:MiscellaneousOtherIncomeExpense
1606	Total other expense (income)	Concept (Monetary)	For Period	Credit	ifrs-full:OtherOperatingIncomeExpense
1607	1154 - Disclosure - Weighted Average Shares Outstanding - Schedule of Basic and Diluted Common Shares Outstanding, Calculated on Weighted Average Basis (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureWeightedAverageSharesOutstandingScheduleOfBasicAndDilutedCommonSharesOutstandingCalculatedOnWeightedAverageBasis
1608	Implied Table	Table	*	*	implied:Table
1609	Earnings per share [abstract]	Abstract			ifrs-full:EarningsPerShareAbstract
1610	Basic shares outstanding	Concept (Shares)	For Period		ifrs-full:WeightedAverageShares
1611	Share options (dilutive effect of 507,066 options; 2017 - 4,426,237 options)	Concept (Shares)	For Period		ifrs-full:DilutiveEffectOfShareOptionsOnNumberOfOrdinaryShares
1612	Diluted shares	Concept (Shares)	For Period		ifrs-full:AdjustedWeightedAverageShares
1613	1155 - Disclosure - Weighted Average Shares Outstanding - Schedule of Basic and Diluted Common Shares Outstanding, Calculated on Weighted Average Basis (Parenthetical) (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureWeightedAverageSharesOutstandingScheduleOfBasicAndDilutedCommonSharesOutstandingCalculatedOnWeightedAverageBasisParenthetical
1614	Implied Table	Table	*	*	implied:Table
1615	Earnings per share [abstract]	Abstract			ifrs-full:EarningsPerShareAbstract
1616	Share options	Concept (Decimal)	As Of		stn:DilutiveShareOptions
1617	1156 - Disclosure - Weighted Average Shares Outstanding - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureWeightedAverageSharesOutstandingAdditionalInformation
1618	Implied Table	Table	*	*	implied:Table
1619	Earnings per share [abstract]	Abstract			ifrs-full:EarningsPerShareAbstract
1620	Antidilutive effect of share options	Concept (Shares)	For Period		stn:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount1
1621	1157 - Disclosure - Cash Flow Information - Reconciliation of Liabilities Arising from Financing Activities (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureCashFlowInformationReconciliationOfLiabilitiesArisingFromFinancingActivities
1622	Disclosure of reconciliation of liabilities arising from financing activities [table]	Table	*	*	ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesTable
1623	Borrowings by name [axis]	Axis			ifrs-full:BorrowingsByNameAxis
1624	Borrowings by name [member]	Member			ifrs-full:BorrowingsByNameMember
1625	Revolving credit facilities [member]	Member			stn:RevolvingCreditFacility1Member
1626	Term loan [member]	Member			stn:TermLoanMember
1627	Liabilities arising from financing activities [axis]	Axis			ifrs-full:LiabilitiesArisingFromFinancingActivitiesAxis
1628	Liabilities arising from financing activities [member]	Member			ifrs-full:LiabilitiesArisingFromFinancingActivitiesMember
1629	Finance lease obligations [member]	Member			ifrs-full:LeaseLiabilitiesMember
1630	Dividends to shareholders [member]	Member			stn:DividendsToShareholdersMember
1631	Disclosure of reconciliation of liabilities arising from financing activities [line items]	LineItems			ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesLineItems
1632	Beginning balance	Concept (Monetary)	As Of	Credit	ifrs-full:LiabilitiesArisingFromFinancingActivities
1633	Statement of Cash Flows, Proceeds	Concept (Monetary)	For Period	Credit	stn:IncreaseDecreaseThroughProceedsLiabilitiesArisingFromFinancingActivities
1634	Statement of Cash Flows, Repayments or Payments	Concept (Monetary)	For Period	Credit	stn:IncreaseDecreaseThroughRepaymentsOrPaymentsLiabilitiesArisingFromFinancingActivities
1635	Non-cash Changes, Foreign Exchange	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughEffectOfChangesInForeignExchangeRatesLiabilitiesArisingFromFinancingActivities
1636	Non-cash Changes, Other	Concept (Monetary)	For Period	Credit	ifrs-full:IncreaseDecreaseThroughOtherChangesLiabilitiesArisingFromFinancingActivities
1637	Ending balance	Concept (Monetary)	As Of	Credit	ifrs-full:LiabilitiesArisingFromFinancingActivities
1638	1158 - Disclosure - Related - Party Disclosures - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRelatedPartyDisclosuresAdditionalInformation
1639	Disclosure of subsidiaries [table]	Table	*	*	ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
1640	Subsidiaries [axis]	Axis			ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1641	Entity's total for subsidiaries [member]	Member			ifrs-full:EntitysTotalForSubsidiariesMember
1642	Wholly owned subsidiaries [member]	Member			stn:WhollyOwnedSubsidiariesMember
1643	Disclosure of subsidiaries [line items]	LineItems			ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
1644	Ownership of voting and restricted securities of non-controlling interest	Concept (Text/String)	For Period		ifrs-full:ExplanationOfRelationshipsBetweenParentsAndEntity
1645	1159 - Disclosure - Related-Party Disclosures - Schedule of Subsidiaries (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRelatedPartyDisclosuresScheduleOfSubsidiaries
1646	Disclosure of subsidiaries [table]	Table	*	*	ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesTable
1647	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
1648	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
1649	3221969 Nova Scotia Company [member]	Member			stn:ThreeTwoTwooneNineSixNineNovaScotiaCompanyMember
1650	International Insurance Group Inc. [member]	Member			stn:InternationalInsuranceGroupIncMember
1651	Mustang Acquisition Holdings Inc. [member]	Member			stn:MustangAcquisitionHoldingsIncMember
1652	MWH International Inc. [member]	Member			stn:MWHInternationalIncMember
1653	Stantec Australia Pty Ltd [member]	Member			stn:StantecAustraliaPtyLtdMember
1654	Stantec Consulting Caribbean Ltd. [member]	Member			stn:StantecConsultingCaribbeanLtdMember
1655	Stantec Consulting International LLC [member]	Member			stn:StantecConsultingInternationalLLCMember
1656	Stantec Consulting International Ltd. [member]	Member			stn:StantecConsultingInternationalLtdMember
1657	Stantec Consulting Ltd./Stantec Experts-conseils ltee [member]	Member			stn:StantecConsultingLtdStantecExpertsconseilsLteeMember
1658	Stantec Consulting Michigan Inc. [member]	Member			stn:StantecConsultingMichiganIncMember
1659	Stantec Consulting Services Inc. [member]	Member			stn:StantecConsultingServicesIncMember
1660	Stantec Delaware II LLC [member]	Member			stn:StantecDelawareIILLCMember
1661	Stantec Holdings (2017) Limited [member]	Member			stn:StantecHoldings2017LimitedMember
1662	Stantec Holdings II Ltd. [member]	Member			stn:StantecHoldingsTwoLtdMember
1663	Stantec New Zealand [member]	Member			stn:StantecNewZealandMember
1664	Stantec Technology International Inc. [member]	Member			stn:StantecTechnologyInternationalIncMember
1665	Stantec UK Limited. [member]	Member			stn:StantecUKLimitedMember
1666	Subsidiaries [axis]	Axis			ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1667	Entity's total for subsidiaries [member]	Member			ifrs-full:EntitysTotalForSubsidiariesMember
1668	Subsidiaries [member]	Member			ifrs-full:SubsidiariesMember
1669	Geographical areas [axis]	Axis			ifrs-full:GeographicalAreasAxis
1670	Geographical areas [member]	Member			ifrs-full:GeographicalAreasMember
1671	Nova Scotia, Canada [member]	Member			stn:NovaScotiaCanadaMember
1672	Barbados [member]	Member			country:BB
1673	Delaware, United States [member]	Member			stpr:DE
1674	Australia [member]	Member			country:AU
1675	Arizona, United States [member]	Member			stpr:AZ
1676	Canada [member]	Member			country:CA
1677	Michigan, United States [member]	Member			stpr:MI
1678	New York, United States [member]	Member			stpr:NY
1679	United Kingdom [member]	Member			country:GB
1680	Alberta, Canada [member]	Member			stn:A0Member
1681	New Zealand [member]	Member			country:NZ
1682	Disclosure of subsidiaries [line items]	LineItems			ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesLineItems
1683	Jurisdiction of Incorporation	Concept (Text/String)	For Period		ifrs-full:CountryOfIncorporationOrResidenceOfSubsidiary
1684	1160 - Disclosure - Related-Party Disclosures - Schedule of Structured Consolidated Entities (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRelatedPartyDisclosuresScheduleOfStructuredConsolidatedEntities
1685	Disclosure Of Significant Consolidated Structure Entities [table]	Table	*	*	stn:DisclosureOfSignificantConsolidatedStructureEntitiesTable
1686	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
1687	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
1688	Stantec Architecture Inc. [member]	Member			stn:StantecArchitectureIncMember
1689	Stantec Architecture Ltd. [member]	Member			stn:StantecArchitectureLtdMember
1690	Stantec Geomatics Ltd. [member]	Member			stn:StantecGeomaticsLtdMember
1691	Stantec International Inc. [member]	Member			stn:StantecInternationalIncMember
1692	Consolidated structured entities [axis]	Axis			ifrs-full:ConsolidatedStructuredEntitiesAxis
1693	Entity's total for consolidated structured entities [member]	Member			ifrs-full:EntitysTotalForConsolidatedStructuredEntitiesMember
1694	Consolidated structured entities [member]	Member			ifrs-full:ConsolidatedStructuredEntitiesMember
1695	Geographical areas [axis]	Axis			ifrs-full:GeographicalAreasAxis
1696	Geographical areas [member]	Member			ifrs-full:GeographicalAreasMember
1697	North Carolina, United States [member]	Member			stpr:NC
1698	Canada [member]	Member			country:CA
1699	Alberta, Canada [member]	Member			stn:A0Member
1700	Pennsylvania, United States [member]	Member			stpr:PA
1701	Disclosure Of Significant Consolidated Structure Entities [Line items]	LineItems			stn:DisclosureOfSignificantConsolidatedStructureEntitiesLineItems
1702	Jurisdiction of Incorporation	Concept (Text/String)	For Period		stn:CountryOfIncorporationOfStructuredEntities
1703	1161 - Disclosure - Related-Party Disclosures - Summary of Joint Operations (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRelatedPartyDisclosuresSummaryOfJointOperations
1704	Disclosure of joint operations [table]	Table	*	*	ifrs-full:DisclosureOfJointOperationsTable
1705	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
1706	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
1707	Stantec/SG Joint Venture [member]	Member			stn:StantecSGJointVentureMember
1708	Starr ll, a Joint Venture [member]	Member			stn:StarrTwoMember
1709	Joint operations [axis]	Axis			ifrs-full:JointOperationsAxis
1710	Entity's total for joint operations [member]	Member			ifrs-full:EntitysTotalForJointOperationsMember
1711	Joint operations [member]	Member			ifrs-full:JointOperationsMember
1712	Geographical areas [axis]	Axis			ifrs-full:GeographicalAreasAxis
1713	Geographical areas [member]	Member			ifrs-full:GeographicalAreasMember
1714	United States [member]	Member			country:US
1715	Disclosure of joint operations [line items]	LineItems			ifrs-full:DisclosureOfJointOperationsLineItems
1716	Ownership Interests	Concept (Percent)	For Period		ifrs-full:ProportionOfOwnershipInterestInJointOperation
1717	Jurisdiction	Concept (Text/String)	For Period		ifrs-full:PrincipalPlaceOfBusinessOfJointOperation
1718	1162 - Disclosure - Related-Party Disclosures - Schedule of Transactions With Related Parties (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRelatedPartyDisclosuresScheduleOfTransactionsWithRelatedParties
1719	Disclosure Of Joint Ventures And Associates [table]	Table	*	*	stn:DisclosureOfJointVenturesAndAssociatesTable
1720	Categories of related parties [axis]	Axis			ifrs-full:CategoriesOfRelatedPartiesAxis
1721	Entity's total for related parties [member]	Member			ifrs-full:EntitysTotalForRelatedPartiesMember
1722	Joint Ventures Where Entity is Venturer [member]	Member			ifrs-full:JointVenturesWhereEntityIsVenturerMember
1723	Associates [member]	Member			ifrs-full:AssociatesMember
1724	Disclosure of transactions between related parties [Line Items]	LineItems			ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
1725	Sales to Related Parties	Concept (Monetary)	For Period	Credit	ifrs-full:RevenueFromRenderingOfServicesRelatedPartyTransactions
1726	Distributions Paid	Concept (Monetary)	For Period	Credit	stn:DistributionPaymentOfRelatedPartyTransaction
1727	Amounts Owed by Related Parties	Concept (Monetary)	As Of	Debit	ifrs-full:AmountsReceivableRelatedPartyTransactions
1728	1163 - Disclosure - Related-Party Disclosures - Schedule of Compensation of Key Management Personnel and Directors of the Company (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureRelatedPartyDisclosuresScheduleOfCompensationOfKeyManagementPersonnelAndDirectorsOfTheCompany
1729	Implied Table	Table	*	*	implied:Table
1730	Disclosure of key management personnel compensation [abstract]	Abstract			stn:DisclosureOfKeyManagementPersonnelCompensationAbstract
1731	Salaries and other short-term employment benefits	Concept (Monetary)	For Period	Debit	ifrs-full:KeyManagementPersonnelCompensationShorttermEmployeeBenefits
1732	Directors' fees	Concept (Monetary)	For Period	Debit	ifrs-full:DirectorsRemunerationExpense
1733	Share-based compensation	Concept (Monetary)	For Period	Debit	ifrs-full:KeyManagementPersonnelCompensationSharebasedPayment
1734	Total compensation	Concept (Monetary)	For Period	Debit	ifrs-full:KeyManagementPersonnelCompensation
1735	1164 - Disclosure - Segmented Information - Schedule of Operating Segments (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureSegmentedInformationScheduleOfOperatingSegments
1736	Disclosure of operating segments [table]	Table	*	*	ifrs-full:DisclosureOfOperatingSegmentsTable
1737	Segments [axis]	Axis			ifrs-full:SegmentsAxis
1738	Segments [member]	Member			ifrs-full:SegmentsMember
1739	Consulting Services Canada [member]	Member			stn:ConsultingServicesCanadaMember
1740	Consulting Services United States [member]	Member			stn:ConsultingServicesUnitedStatesMember
1741	Consulting Services Global [member]	Member			stn:ConsultingServicesGlobalMember
1742	Segment consolidation items [axis]	Axis			ifrs-full:SegmentConsolidationItemsAxis
1743	Entity's total for segment consolidation items [member]	Member			ifrs-full:EntitysTotalForSegmentConsolidationItemsMember
1744	Adjustments and Eliminations [member]	Member			ifrs-full:EliminationOfIntersegmentAmountsMember
1745	Total Segments [member]	Member			ifrs-full:OperatingSegmentsMember
1746	Disclosure of operating segments [line items]	LineItems			ifrs-full:DisclosureOfOperatingSegmentsLineItems
1747	Gross revenue	Concept (Monetary)	For Period	Credit	stn:GrossRevenue
1748	Gross revenue	Concept (Monetary)	For Period	Credit	ifrs-full:Revenue
1749	Gross revenue	Concept (Monetary)	For Period	Credit	stn:RevenueFromContinuingOperations
1750	Less subconsultants and other direct expenses	Concept (Monetary)	For Period	Debit	stn:SubconsultantSubcontractorAndOtherDirectExpenses
1751	Net revenue	Concept (Monetary)	For Period	Credit	stn:NetRevenue
1752	Gross margin	Concept (Monetary)	For Period	Credit	ifrs-full:GrossProfit
1753	1165 - Disclosure - Segmented Information - Schedule of Non-Current Assets and Gross Revenue by Geographical Areas (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureSegmentedInformationScheduleOfNonCurrentAssetsAndGrossRevenueByGeographicalAreas
1754	Disclosure of geographical areas [table]	Table	*	*	ifrs-full:DisclosureOfGeographicalAreasTable
1755	Geographical areas [axis]	Axis			ifrs-full:GeographicalAreasAxis
1756	Geographical areas [member]	Member			ifrs-full:GeographicalAreasMember
1757	Canada [member]	Member			country:CA
1758	United States [member]	Member			country:US
1759	United Kingdom [member]	Member			country:GB
1760	Other Countries [member]	Member			stn:OtherCountriesMember
1761	Disclosure of geographical areas [line items]	LineItems			ifrs-full:DisclosureOfGeographicalAreasLineItems
1762	Non-current assets	Concept (Monetary)	As Of	Debit	ifrs-full:NoncurrentAssetsOtherThanFinancialInstrumentsDeferredTaxAssetsPostemploymentBenefitAssetsAndRightsArisingUnderInsuranceContracts
1763	Gross revenue	Concept (Monetary)	For Period	Credit	ifrs-full:Revenue
1764	1166 - Disclosure - Segmented Information - Schedule of Gross Revenue by Services (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureSegmentedInformationScheduleOfGrossRevenueByServices
1765	Disclosure of geographical areas [table]	Table	*	*	ifrs-full:DisclosureOfGeographicalAreasTable
1766	Segments [axis]	Axis			ifrs-full:SegmentsAxis
1767	Segments [member]	Member			ifrs-full:SegmentsMember
1768	Consulting Services [member]	Member			stn:ConsultingServicesMember
1769	Products and services [axis]	Axis			ifrs-full:ProductsAndServicesAxis
1770	Products and services [member]	Member			ifrs-full:ProductsAndServicesMember
1771	Buildings Services [member]	Member			stn:BuildingsServicesMember
1772	Energy and Resources Services [member]	Member			stn:EnergyAndResourcesServicesMember
1773	Environmental Services [member]	Member			stn:EnvironmentalServicesMember
1774	Infrastructure [member]	Member			stn:InfrastructureMember
1775	Water Services [member]	Member			stn:WaterServicesMember
1776	Disclosure of products and services [line items]	LineItems			ifrs-full:DisclosureOfProductsAndServicesLineItems
1777	Gross revenue	Concept (Monetary)	For Period	Credit	ifrs-full:Revenue
1778	1167 - Disclosure - Segmented Information - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureSegmentedInformationAdditionalInformation
1779	Implied Table	Table	*	*	implied:Table
1780	Disclosure of operating segments [abstract]	Abstract			ifrs-full:DisclosureOfOperatingSegmentsAbstract
1781	Information about major customers	Concept (Text/String)	For Period		ifrs-full:InformationAboutMajorCustomers
1782	1168 - Disclosure - Investment Tax Credit - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureInvestmentTaxCreditAdditionalInformation
1783	Implied Table	Table	*	*	implied:Table
1784	Investment tax credits [abstract]	Abstract			stn:InvestmentTaxCreditsAbstract
1785	Investment tax credits	Concept (Monetary)	For Period	Credit	stn:InvestmentTaxCredits
1786	1169 - Disclosure - Events after the Reporting Period - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureEventsAfterTheReportingPeriodAdditionalInformation
1787	Disclosure of non-adjusting events after reporting period [table]	Table	*	*	ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodTable
1788	Non-adjusting events after reporting period [axis]	Axis			ifrs-full:NonadjustingEventsAfterReportingPeriodAxis
1789	Non-adjusting events after reporting period [member]	Member			ifrs-full:NonadjustingEventsMember
1790	Dividend transaction [member]	Member			stn:DividendTransactionMember
1791	Events after reporting period [member]	Member			stn:EventsAfterReportingPeriodMember
1792	Classes of ordinary shares [axis]	Axis			ifrs-full:ClassesOfOrdinarySharesAxis
1793	Ordinary Shares [Member]	Member			ifrs-full:OrdinarySharesMember
1794	Normal Course Issuer Bid (NCIB) [member]	Member			stn:NCIBMember
1795	Disclosure of non-adjusting events after reporting period [Line Items]	LineItems			ifrs-full:DisclosureOfNonadjustingEventsAfterReportingPeriodLineItems
1796	Number of Common shares repurchased and cancelled	Concept (Shares)	For Period		stn:NumberOfCommonSharesRepurchasedAndCancelled
1797	Average price of common shares repurchased and cancelled	Concept (Share)	For Period		stn:AveragePriceOfCommonSharesRepurchasedAndCancelled
1798	Aggregate price of common shares repurchased and cancelled	Concept (Monetary)	For Period	Credit	ifrs-full:CancellationOfTreasuryShares
1799	Agreement expiry date	Concept (Date)	For Period		stn:AgreementExpiryDate
1800	Interest rate swap agreement, Amount	Concept (Monetary)	For Period	Credit	stn:InterestRateSwapAgreementAmount
1801	Interest rate swap agreement, Fixed Interest rate	Concept (Percent)	For Period		stn:InterestRateSwapAgreementFixedInterestRate
1802	Interest rate swap, description	Concept (Text/String)	For Period		stn:InterestRateSwapDescription
1803	Dividends payable declared date	Concept (Date)	For Period		stn:DividendsPayableDeclaredDate
1804	Dividends payable amount per share	Concept (Share)	For Period		ifrs-full:DividendsProposedOrDeclaredBeforeFinancialStatementsAuthorisedForIssueButNotRecognisedAsDistributionToOwnersPerShare
1805	Dividend payable date	Concept (Date)	For Period		stn:DividendPayableDate
1806	Dividends payable record date	Concept (Date)	For Period		stn:DividendsPayableRecordDate
1807	1170 - Disclosure - Comparative Figures - Additional Information (Detail)	Network	*	*	http://www.stantec.com/taxonomy/role/DisclosureComparativeFiguresAdditionalInformation
1808	Implied Table	Table	*	*	implied:Table
1809	Disclosure of reclassifications or changes in presentation [abstract]	Abstract			ifrs-full:DisclosureOfReclassificationsOrChangesInPresentationAbstract
1810	Employee defined benefit liability	Concept (Monetary)	As Of	Credit	stn:NetEmployeeDefinedBenefitLiability