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

Represents the cash EPS compound annual growth rate performance period under the sharebased payment arrangement.

No definition available.

Name:	wbk_SharebasedPaymentArrangementCashEpsCompoundAnnualGrowthRatePerformancePeriod
Namespace Prefix:	wbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The cost of shares allocated.

No definition available.

Name:	wbk_SharebasedPaymentArrangementCostOfSharesAllocated
Namespace Prefix:	wbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the holding lock period under the sharebased payment arrangement.

No definition available.

Name:	wbk_SharebasedPaymentArrangementHoldingLockPeriod
Namespace Prefix:	wbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the performance period under the sharebased payment arrangement.

No definition available.

Name:	wbk_SharebasedPaymentArrangementPerformancePeriod
Namespace Prefix:	wbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the share retention period under the sharebased payment arrangement.

No definition available.

Name:	wbk_SharebasedPaymentArrangementServiceConditionShareRetentionPeriod
Namespace Prefix:	wbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	wbk_SharebasedPaymentArrangementVestingPeriod
Namespace Prefix:	wbk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the threshold amount up to which shares are allocated free of cost per employee.

No definition available.

Name:	wbk_ThresholdPriceOfSharesAllocatedToEmployees
Namespace Prefix:	wbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The weighted average exercise price of other equity instruments (ie other than share options) outstanding in a share-based payment arrangement.

No definition available.

Name:	wbk_WeightedAverageExercisePriceOfOtherEquityInstrumentsOutstandingInShareBasedPaymentArrangement2019
Namespace Prefix:	wbk_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=wbk_WestpacLongTermIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	wbk_IfrsAwardDateAxis=wbk_AwardDates2011To2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	wbk_IfrsAwardDateAxis=wbk_AwardDatesIn2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	wbk_IfrsAwardTypeAxis=wbk_ShareRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=wbk_WestpacPerformancePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=wbk_RestrictedSharePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: