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Covered Assets - Credit Risk Profile by Internally Assigned Grade by Loan Status Designation (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014
Covered Assets, Loan Status Designation [Line Items]
Covered loans, gross	$ 192,637wfsl_LoansAndLeasesReceivableCoveredLoansGross	$ 213,203wfsl_LoansAndLeasesReceivableCoveredLoansGross
Discount balance related to acquired loans	(28,916)us-gaap_ReceivableWithImputedInterestDiscount	(34,483)us-gaap_ReceivableWithImputedInterestDiscount
Covered loans, allowance for losses	(2,243)wfsl_CoveredLoansAllowanceForLosses	(2,244)wfsl_CoveredLoansAllowanceForLosses
Loans and Leases Receivable, Covered Loans, Net Reported Amount	161,478wfsl_LoansAndLeasesReceivableCoveredLoansNetReportedAmount	176,476wfsl_LoansAndLeasesReceivableCoveredLoansNetReportedAmount
Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	83,445wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember	100,161wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember
Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	109,192wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember	113,042wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember
Single-Family Residential [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	21,876wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember	23,067wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Land - Acquisition & Development [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	389wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember	1,364wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember
Land - Consumer Lot Loans [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	73wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember	73wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember
Multi-Family [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	4,250wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember	6,598wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember
Commercial Real Estate [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	40,127wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember	51,336wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial & Industrial [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	5,111wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember	5,492wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember
HELOC [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	11,226wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember	11,777wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember
Consumer [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	393wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember	454wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Pool 1 - Construction and Land, Acquisition and Development [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	19,270wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember	20,261wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember
Pool 2 - Single-Family Residential [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	15,385wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember	15,964wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember
Pool 3 - Multi-family [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	491wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember	523wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember
Pool 4 - Home Equity Line of Credit and Other Consumer Loans [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	3,939wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember	3,977wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember
Pool 5 - Commercial Real Estate [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	62,672wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember	64,391wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember
Pool 6 - Commercial and Industrial [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	7,435wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember	7,926wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember
Pass [Member]
Covered Assets, Loan Status Designation [Line Items]
Grade as percentage of total gross loans	97.00%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	97.20%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	64,752wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	70,926wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Grade as percentage of total gross loans	77.60%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	70.80%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	61,680wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	64,208wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Single-Family Residential [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	20,664wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	21,311wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Land - Acquisition & Development [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	353wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	972wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Land - Consumer Lot Loans [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	73wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	73wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Multi-Family [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	4,250wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	6,598wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Commercial Real Estate [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	25,317wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	26,940wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Commercial & Industrial [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	2,476wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	2,801wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | HELOC [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	11,226wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	11,777wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Consumer [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	393wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	454wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Pool 1 - Construction and Land, Acquisition and Development [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	7,128wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	8,349wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Pool 2 - Single-Family Residential [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	15,061wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	15,585wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Pool 3 - Multi-family [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	51wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	52wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Pool 4 - Home Equity Line of Credit and Other Consumer Loans [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	2,772wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	2,804wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Pool 5 - Commercial Real Estate [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	33,543wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	33,909wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Pool 6 - Commercial and Industrial [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	3,125wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember	3,509wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Special Mention [Member]
Covered Assets, Loan Status Designation [Line Items]
Grade as percentage of total gross loans	0.40%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0.40%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	115wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Grade as percentage of total gross loans	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0.10%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	692wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	700wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Single-Family Residential [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Land - Acquisition & Development [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Land - Consumer Lot Loans [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Multi-Family [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Commercial Real Estate [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	115wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Commercial & Industrial [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | HELOC [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Consumer [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Pool 1 - Construction and Land, Acquisition and Development [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Pool 2 - Single-Family Residential [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Pool 3 - Multi-family [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Pool 4 - Home Equity Line of Credit and Other Consumer Loans [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Pool 5 - Commercial Real Estate [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	692wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	700wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Pool 6 - Commercial and Industrial [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Substandard [Member]
Covered Assets, Loan Status Designation [Line Items]
Grade as percentage of total gross loans	2.60%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	2.40%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	18,693wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	29,120wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Grade as percentage of total gross loans	22.40%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	29.10%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	46,303wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	47,609wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Single-Family Residential [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	1,212wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	1,756wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Land - Acquisition & Development [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	36wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	392wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Land - Consumer Lot Loans [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Multi-Family [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Commercial Real Estate [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	14,810wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	24,281wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Commercial & Industrial [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	2,635wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	2,691wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | HELOC [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Consumer [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Pool 1 - Construction and Land, Acquisition and Development [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	12,142wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	11,912wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Pool 2 - Single-Family Residential [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	324wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	379wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Pool 3 - Multi-family [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	440wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	471wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Pool 4 - Home Equity Line of Credit and Other Consumer Loans [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	1,167wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	1,173wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Pool 5 - Commercial Real Estate [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	28,437wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	29,782wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Pool 6 - Commercial and Industrial [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	3,793wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember	3,892wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Doubtful [Member]
Covered Assets, Loan Status Designation [Line Items]
Grade as percentage of total gross loans	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Grade as percentage of total gross loans	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	517wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	525wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Single-Family Residential [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Land - Acquisition & Development [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Land - Consumer Lot Loans [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Multi-Family [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Commercial Real Estate [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Commercial & Industrial [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | HELOC [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Consumer [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Pool 1 - Construction and Land, Acquisition and Development [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Pool 2 - Single-Family Residential [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Pool 3 - Multi-family [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Pool 4 - Home Equity Line of Credit and Other Consumer Loans [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Pool 5 - Commercial Real Estate [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Pool 6 - Commercial and Industrial [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	517wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember	525wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Loss [Member]
Covered Assets, Loan Status Designation [Line Items]
Grade as percentage of total gross loans	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Grade as percentage of total gross loans	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0.00%wfsl_GradeAsPercentageOfTotalGrossLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Single-Family Residential [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Land - Acquisition & Development [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandAcquisitionAndDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Land - Consumer Lot Loans [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_LandConsumerLotLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Multi-Family [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_MultiFamilyHousingPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Commercial Real Estate [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Commercial & Industrial [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_CommercialAndIndustrialLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | HELOC [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_HomeEquityLineOfCreditMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Consumer [Member] | Acquired Non Impaired Assets [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredNonImpairedAssetsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Pool 1 - Construction and Land, Acquisition and Development [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Pool 2 - Single-Family Residential [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool2SingleFamilyResidentialMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Pool 3 - Multi-family [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool3MultifamilyMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Pool 4 - Home Equity Line of Credit and Other Consumer Loans [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Pool 5 - Commercial Real Estate [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool5CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember
Loss [Member] | Pool 6 - Commercial and Industrial [Member] | Acquired Impaired Loans [Member]
Covered Assets, Loan Status Designation [Line Items]
Amount of Loans Net of LIP & Chg.-Offs	$ 0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember	$ 0wfsl_LoansAndLeasesReceivableCoveredLoans / wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis = wfsl_AcquiredImpairedLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = wfsl_Pool6CommercialandIndustrialMember / us-gaap_InternalCreditAssessmentAxis = wfsl_LossMember

X

- Definition

Disclosure of the unamortized amount of the discount on the note or receivable which is deducted from the face amount of the receivable or loan. The discount or premium is the difference between the present value and the face amount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

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Namespace Prefix:	wfsl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Covered Loans, Allowance for Losses

+ References

No definition available.

+ Details

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Namespace Prefix:	wfsl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Grade as Percentage of Total Gross Loans

+ References

No definition available.

+ Details

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

X

- Definition

Loans and Leases Receivable, Covered Loans, Gross

+ References

No definition available.

+ Details

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Namespace Prefix:	wfsl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Loans and Leases Receivable, Covered Loans, Gross

+ References

No definition available.

+ Details

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Namespace Prefix:	wfsl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Loans and Leases Receivable, Covered Loans, Net Reported Amount

+ References

No definition available.

+ Details

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Namespace Prefix:	wfsl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_CommercialAndIndustrialLoansMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_HomeEquityLineOfCreditMember
Namespace Prefix:
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_LandAcquisitionAndDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_LandConsumerLotLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_MultiFamilyHousingPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_Pool1ConstructionandLandAcquisitionandDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_Pool2SingleFamilyResidentialMember
Namespace Prefix:
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_Pool3MultifamilyMember
Namespace Prefix:
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_Pool4HomeEquityLineofCreditandOtherConsumerLoansMember
Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wfsl_Pool6CommercialandIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_DoubtfulMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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- Details

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Namespace Prefix:
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Balance Type:
Period Type:

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- Details

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Balance Type:
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- Details

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Namespace Prefix:
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Balance Type:
Period Type:

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- Details

Name:	us-gaap_InternalCreditAssessmentAxis=wfsl_LossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	wfsl_CoveredAssetsStatusOfLoansAcquiredInTransferAxis=wfsl_AcquiredImpairedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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- Details

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Namespace Prefix:
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