XML 120 R78.htm IDEA: XBRL DOCUMENT
v3.20.2

Revenue from Contracts with Customers (Details) | 12 Months Ended
--- | ---
Sep. 30, 2020 | Sep. 30, 2019
Revenue from Contract with Customer [Abstract] |  |
Revenue streams percentage, contract with customer | 5.10% | 5.00%

X
- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Revenue From Contract With Customer, Percentage + References No definition available. + Details
Name: | wfsl_RevenueFromContractWithCustomerPercentage
Namespace Prefix: | wfsl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration