CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 64,560	$ 61,775	$ 138,901	$ 207,218
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) during the period on available-for-sale investment securities, net of tax of $(699) and $2,350	4,790	(7,822)	34,336	5,649
Reclassification adjustment of net (gain) loss from sale of available-for-sale securities included in net income, net of tax of $(20) and $(1)	60	3	193	3
Net unrealized gain (loss) from investment securities, net of reclassification adjustment	4,850	(7,819)	34,529	5,652
Net unrealized gain (loss) during the period on borrowings cash flow hedges, net of tax of $1,387 and $(3,409)	(1,869)	11,348	(26,534)	(10,782)
Net unrealized gain (loss) in cash flow hedging instruments, net of reclassification adjustment	(1,869)	11,348	(26,534)	(10,782)
Other comprehensive income (loss)	2,981	3,529	7,995	(5,130)
Comprehensive income	$ 67,541	$ 65,304	$ 146,896	$ 202,088