XML 20 R37.htm IDEA: XBRL DOCUMENT v2.4.1.9
Allowance for Losses on Loans - Internally Assigned Grade (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Sep. 30, 2014
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross $ 8,793,428us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 8,669,717us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 8,527,567us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 8,423,666us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
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
Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 34,511us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 37,860us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
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
Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 231,329us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 208,133us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
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
Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 21us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 58us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
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
Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
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
Single-Family Residential [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 5,619,694us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 5,572,244us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Construction - Speculative [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 152,450us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember		 140,060us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
Construction - Custom [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 377,561us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember		 385,824us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
Land - Acquisition & Development [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 86,405us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember		 80,359us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember
Land - Consumer Lot Loans [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 106,988us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember		 111,130us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
Multi-Family [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 980,706us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember		 920,285us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 749,856us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 752,957us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial & Industrial [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 453,418us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember		 434,088us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
HELOC [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 134,998us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember		 134,455us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember
Consumer [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 131,352us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 138,315us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Non-Acquired Loans [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 8,538,202us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember		 8,409,022us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
Non-Acquired Loans [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 8,308,732us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 8,205,380us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 17,965us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 19,504us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 211,505us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 184,138us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Single-Family Residential [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 5,608,208us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 5,560,203us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Non-Acquired Loans [Member] | Single-Family Residential [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 5,484,864us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 5,426,895us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Single-Family Residential [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,357us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 2,793us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Single-Family Residential [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 120,987us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 130,515us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Single-Family Residential [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Single-Family Residential [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Construction - Speculative [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 152,450us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember		 140,060us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
Non-Acquired Loans [Member] | Construction - Speculative [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 147,979us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 134,950us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Construction - Speculative [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Construction - Speculative [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 4,471us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 5,110us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Construction - Speculative [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Construction - Speculative [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionSpeculativeMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Construction - Custom [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 377,561us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember		 385,824us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
Non-Acquired Loans [Member] | Construction - Custom [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 377,561us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 385,824us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Construction - Custom [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Construction - Custom [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Construction - Custom [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | Construction - Custom [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
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= wfsl_ConstructionCustomMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Land - Acquisition & Development [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 84,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember		 77,832us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
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= wfsl_LandAcquisitionAndDevelopmentMember
Non-Acquired Loans [Member] | Land - Acquisition & Development [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 78,428us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 71,692us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
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= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | Land - Acquisition & Development [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Land - Acquisition & Development [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 5,572us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 6,140us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Land - Acquisition & Development [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | Land - Acquisition & Development [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= wfsl_LandAcquisitionAndDevelopmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 104,492us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember		 108,623us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 103,890us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 108,013us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 602us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 610us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Multi-Family [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 977,752us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember		 917,286us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
Non-Acquired Loans [Member] | Multi-Family [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 971,647us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 912,728us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Multi-Family [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Multi-Family [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 6,105us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 4,558us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Multi-Family [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Multi-Family [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= wfsl_MultiFamilyHousingPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 597,436us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 591,336us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Non-Acquired Loans [Member] | Commercial Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 566,553us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 557,914us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 1,955us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 1,971us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 28,928us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 31,451us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Commercial Real Estate [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Commercial & Industrial [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 391,327us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember		 379,226us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
Non-Acquired Loans [Member] | Commercial & Industrial [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 333,082us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 359,221us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Non-Acquired Loans [Member] | Commercial & Industrial [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 13,653us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 14,740us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Commercial & Industrial [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 44,592us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 5,265us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Non-Acquired Loans [Member] | Commercial & Industrial [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Commercial & Industrial [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_CommercialAndIndustrialLoansMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | HELOC [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 118,047us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember		 116,042us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= wfsl_HomeEquityLineOfCreditMember
Non-Acquired Loans [Member] | HELOC [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 117,799us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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Non-Acquired Loans [Member] | HELOC [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | HELOC [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 248us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | HELOC [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
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/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | HELOC [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Consumer [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 126,929us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 132,590us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= us-gaap_ConsumerPortfolioSegmentMember
Non-Acquired Loans [Member] | Consumer [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 126,929us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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Non-Acquired Loans [Member] | Consumer [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_BusinessAcquisitionAxis
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= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Non-Acquired Loans [Member] | Consumer [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 241us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
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Non-Acquired Loans [Member] | Consumer [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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= us-gaap_DoubtfulMember
Non-Acquired Loans [Member] | Consumer [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 180,572us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember		 181,355us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
Acquired Loans [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 158,844us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 156,954us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Acquired Loans [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 13,743us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 16,213us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Acquired Loans [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 7,964us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 8,130us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 21us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 58us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Single-Family Residential [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 11,163us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Acquired Loans [Member] | Single-Family Residential [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 11,163us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Single-Family Residential [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Single-Family Residential [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
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Acquired Loans [Member] | Single-Family Residential [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Single-Family Residential [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Land - Acquisition & Development [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 872us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 479us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Land - Acquisition & Development [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
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/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Land - Acquisition & Development [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 393us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member] | Land - Acquisition & Development [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Land - Acquisition & Development [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Land - Consumer Lot Loans [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,496us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,496us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_InternalCreditAssessmentAxis
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/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,954us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,954us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 742us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Commercial Real Estate [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
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Acquired Loans [Member] | Commercial & Industrial [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 58,836us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Commercial & Industrial [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Commercial & Industrial [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Commercial & Industrial [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 171us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Commercial & Industrial [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 21us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
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Acquired Loans [Member] | Commercial & Industrial [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
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Acquired Loans [Member] | HELOC [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 7,749us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | HELOC [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | HELOC [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
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Acquired Loans [Member] | HELOC [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | HELOC [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Consumer [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 4,369us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | Consumer [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 4,369us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Consumer [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Consumer [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Consumer [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 60,287us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 11,571us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial & Industrial [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial & Industrial [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial & Industrial [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial & Industrial [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial & Industrial [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial & Industrial [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Credit Impaired Acquired Loans [Member] | HELOC [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Consumer [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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