XML 49 R39.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Fair Value Measurements - Additional Information (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2016 | Jun. 30, 2015 | Jun. 30, 2016 | Jun. 30, 2015
Fair Value Disclosures [Abstract] |  |  |  |
Proceeds from sale of available-for-sale securities, net | $ 0 | $ 235,110,000 | $ 0 | $ 235,110,000
Gross realized gain (loss) on AFS |  | $ 9,639,000 |  | $ 9,639,000
Term of contractual due dates of substantially all mortgage-backed securities (in years) |  |  | 10 years |

X
- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Proceeds from Sale of Available-for-sale Securities, Net + References No definition available. + Details
Name: | wfsl_ProceedsfromSaleofAvailableforsaleSecuritiesNet
Namespace Prefix: | wfsl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Term of Contractual Due Dates of Substantially All Mortgage-Backed Securities + References No definition available. + Details
Name: | wfsl_TermOfContractualDueDatesOfSubstantiallyAllMortgageBackedSecurities
Namespace Prefix: | wfsl_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration