Name:	ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The gain on the recovery of loans and advances previously written off.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 85
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_85&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_GainOnRecoveryOfLoansAndAdvancesPreviouslyWrittenOff
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount of impairment loss recognised in profit or loss for loans and advances. [Refer: Impairment loss recognised in profit or loss]

Name:	ifrs-full_ImpairmentLossRecognisedInProfitOrLossLoansAndAdvances
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

The amount of impairment loss or reversal of impairment loss recognised in profit or loss for loans and advances. [Refer: Impairment loss recognised in profit or loss; Reversal of impairment loss recognised in profit or loss]

Name:	ifrs-full_ImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossLoansAndAdvances
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of reversal of impairment loss recognised in profit or loss for loans and advances. [Refer: Reversal of impairment loss recognised in profit or loss]

Name:	ifrs-full_ReversalOfImpairmentLossRecognisedInProfitOrLossLoansAndAdvances
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

Name:	ifrs-full_InitiallyAppliedIFRSsAxis=wbk_Aasb9MeasurementBasisMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_RiskExposuresAxis=wbk_PerformingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_RiskExposuresAxis=wbk_NonPerformingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=wbk_LoansAndCreditCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=wbk_DebtSecuritiesAtAmortisedCostMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=wbk_DebtSecuritiesAtFairValueThroughOtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_InitiallyAppliedIFRSsAxis=wbk_Aasb139MeasurementBasisMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_MethodOfAssessmentOfExpectedCreditLossesAxis=ifrs-full_ExpectedCreditLossesIndividuallyAssessedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_MethodOfAssessmentOfExpectedCreditLossesAxis=ifrs-full_ExpectedCreditLossesCollectivelyAssessedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: