Financial Information - WAFD, Inc.. - Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income
Total Income	$ 1,042,955	$ 666,359	$ 591,610
Expense
Income before income taxes	325,076	300,037	233,138
Income tax benefit (expense)	(67,650)	(63,707)	(49,523)
Net income	257,426	236,330	183,615
Dividends on preferred stock	14,625	14,625	10,034
Net income available to common shareholders	242,801	221,705	173,581
Net income available to common shareholders	242,801	221,705	173,581
Parent Company
Income
Dividends from subsidiary	56,490	172,850	92,400
Total Income	56,490	172,850	92,400
Expense
Miscellaneous expense	2,214	619	626
Total expense	2,214	619	626
Net income (loss) before equity in undistributed net income (loss) of subsidiary	54,276	172,231	91,774
Equity in undistributed net income (loss) of subsidiaries	202,643	63,956	91,697
Income before income taxes	256,919	236,187	183,471
Income tax benefit (expense)	507	143	144
Net income	257,426	236,330	183,615
Dividends on preferred stock	14,625	14,625	10,034
Net income available to common shareholders	242,801	221,705	173,581
Net income available to common shareholders	$ 242,801	$ 221,705	$ 173,581