| Document and Entity Information | Feb. 14, 2023 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 14, 2023 |
| Entity Registrant Name | WASHINGTON FEDERAL INC |
| Entity Central Index Key | 0000936528 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | WA |
| Entity File Number | 001-34654 |
| Entity Tax Identification Number | 91-1661606 |
| Entity Address, Address Line One | 425 Pike Street |
| Entity Address, City or Town | Seattle |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98101 |
| City Area Code | 206 |
| Local Phone Number | 624-7930 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Series A Preferred Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares, Each Representing a 1/40th Interest in a Share of 4.875% Fixed Rate Series A Non-Cumulative Perpetual Preferred Stock |
| Trading Symbol | WAFDP |
| Security Exchange Name | NASDAQ |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, $1.00 par value per share |
| Trading Symbol | WAFD |
| Security Exchange Name | NASDAQ |
