Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18794-111554

Name:	us-gaap_LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Financing Receivables, Percent of Troubled Debt Restructuring Classified as Performing

No definition available.

Name:	wfsl_FinancingReceivablesPercentofTroubledDebtRestructuringClassifiedasPerforming
Namespace Prefix:	wfsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Loan Modification, Basis Point Reduction, Maximum

No definition available.

Name:	wfsl_LoanModificationBasisPointReductionMaximum
Namespace Prefix:	wfsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Loan Modification, Basis Point Reduction, Minimum

No definition available.

Name:	wfsl_LoanModificationBasisPointReductionMinimum
Namespace Prefix:	wfsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Loans and Leases Receivable, Ratio of Total Past Due Loans to Total Loans Receivable, Net of Charge Offs and Loans in Process

No definition available.

Name:	wfsl_LoansAndLeasesReceivableRatioOfTotalPastDueLoansToTotalLoansReceivableNetOfChargeOffsAndLoansInProcess
Namespace Prefix:	wfsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Loans and Leases Receivable, Impaired, Nonperforming, Nonaccrual Interest Income Recognized

No definition available.

Name:	wfsl_LoansandLeasesReceivableImpairedNonperformingNonaccrualInterestIncomeRecognized
Namespace Prefix:	wfsl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Single Family Residential Loans as Percentage of Restructured Loans

No definition available.

Name:	wfsl_SingleFamilyResidentialLoansAsPercentageOfRestructuredLoans
Namespace Prefix:	wfsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Term for Payment and Rate Reduction

No definition available.