Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2019	Apr. 29, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Registrant Name	WASHINGTON FEDERAL INC
Entity Central Index Key	0000936528
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		80,442,401