Cover Page - shares	6 Months Ended
	Mar. 31, 2023	Apr. 30, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
Document Transition Report	false
Entity File Number	001-34654
Entity Registrant Name	WASHINGTON FEDERAL INC
Entity Incorporation, State or Country Code	WA
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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		65,792,216
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000936528
Current Fiscal Year End Date	--09-30
Common Stock, $1.00 par value per share
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $1.00 par value per share
Trading Symbol	WAFD
Security Exchange Name	NASDAQ
Depositary Shares, Each Representing a 1/40th Interest in a Share of 4.875% Fixed Rate Series A Non-Cumulative Perpetual 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