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
Mar. 31, 2015
Sep. 30, 2014
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross $ 9,014,755us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 8,669,717us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 8,800,830us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 8,423,666us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Total grade as a % of total net loans 97.60%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 20,449us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 37,860us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Total grade as a % of total net loans 0.20%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 188,607us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 208,133us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Total grade as a % of total net loans 2.10%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 4,869us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 58us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Total grade as a % of total net loans 0.10%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
Total grade as a % of total net 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 5,546,403us-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 163,657us-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 370,693us-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 107,181us-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 104,558us-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 1,012,915us-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 885,177us-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 466,207us-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 136,439us-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 221,525us-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 8,775,673us-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 8,581,884us-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 16,292us-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 172,628us-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 4,869us-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 5,535,104us-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 5,426,579us-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 2,343us-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 106,182us-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 163,657us-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 157,847us-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 5,810us-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 370,693us-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 370,693us-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
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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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/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Land - Acquisition & Development [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 105,058us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandAcquisitionAndDevelopmentMember		 77,832us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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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 99,686us-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
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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
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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 5,372us-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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/ 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
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= 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 102,082us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember		 108,623us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
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= wfsl_LandConsumerLotLoansMember
Non-Acquired Loans [Member] | Land - Consumer Lot Loans [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 101,505us-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 577us-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
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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 1,010,003us-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 1,004,149us-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
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/ 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 5,854us-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
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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 741,137us-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 728,274us-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 0us-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 12,863us-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
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/ 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 408,358us-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 353,998us-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 13,949us-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 35,542us-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 4,869us-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
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/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | HELOC [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 120,901us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Non-Acquired Loans [Member] | HELOC [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 120,653us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_HomeEquityLineOfCreditMember
/ us-gaap_InternalCreditAssessmentAxis
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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
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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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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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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
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/ us-gaap_InternalCreditAssessmentAxis
= wfsl_LossMember
Non-Acquired Loans [Member] | Consumer [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 218,680us-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 218,500us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ 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
= wfsl_NonAcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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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 180us-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_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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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
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 169,559us-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 160,927us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 156,954us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,384us-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
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Acquired Loans [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 6,248us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 8,130us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_InternalCreditAssessmentAxis
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Acquired Loans [Member] | Doubtful [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] | 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] | Single-Family Residential [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 10,977us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 11,716us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Single-Family Residential [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 10,977us-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
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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
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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 728us-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 343us-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 385us-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] | 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 2,476us-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 2,476us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= wfsl_AcquiredLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wfsl_LandConsumerLotLoansMember
/ 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
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= 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
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,912us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
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Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
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Acquired Loans [Member] | Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Acquired Loans [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 514us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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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
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Acquired Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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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
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Acquired Loans [Member] | Commercial & Industrial [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] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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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
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Acquired Loans [Member] | Commercial & Industrial [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 123us-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 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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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
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Acquired Loans [Member] | HELOC [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 6,700us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Acquired Loans [Member] | HELOC [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
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Financing Receivable, Recorded Investment [Line Items]    
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Acquired Loans [Member] | HELOC [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Acquired Loans [Member] | Consumer [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 2,794us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
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Financing Receivable, Recorded Investment [Line Items]    
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/ 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
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Acquired Loans [Member] | Consumer [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Loans receivable, gross 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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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] | HELOC & Other Consumer [Member] | Loss [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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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]    
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Substandard [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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Credit Impaired Acquired Loans [Member] | Commercial Real Estate [Member] | Doubtful [Member]    
Financing Receivable, Recorded Investment [Line Items]    
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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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Financing Receivable, Recorded Investment [Line Items]    
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Financing Receivable, Recorded Investment [Line Items]    
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Financing Receivable, Recorded Investment [Line Items]    
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Financing Receivable, Recorded Investment [Line Items]    
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