XML 91 R69.htm IDEA: XBRL DOCUMENT
v3.8.0.1

FHLB Advances and Other Borrowings - Additional Information (Details) | 12 Months Ended
--- | ---
Sep. 30, 2017
Federal Home Loan Bank of Des Moines |
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items] |
Federal home loan bank, percent of assets | 48.00%

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Federal Home Loan Bank, Line of Credit, Maximum Borrowing Capacity, Percentage of Assets + References No definition available. + Details
Name: | wfsl_FederalHomeLoanBankLineofCreditMaximumBorrowingCapacityPercentageofAssets
Namespace Prefix: | wfsl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis=us-gaap_FederalHomeLoanBankOfDesMoinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |