CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 63,295	$ 47,422	$ 162,935	$ 131,244
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) during the period on available-for-sale investment securities, net of tax	(41,158)	2,027	(87,859)	7,289
Reclassification adjustment of net (gain) loss from sale of available-for-sale securities included in net income, net of tax	0	0	62	0
Net unrealized gain (loss) from investment securities, net of reclassification adjustment	(41,158)	2,027	(87,797)	7,289
Net unrealized gain (loss) during the period on borrowings cash flow hedges, net of tax	23,907	(18,083)	72,239	51,743
Reclassification adjustment of net (gain) loss included in net income during the period from hedging derivatives, net of tax	0	0	0	(10,865)
Net unrealized gain (loss) in cash flow hedging instruments, net of reclassification adjustment	23,907	(18,083)	72,239	40,878
Other comprehensive income (loss)	(17,251)	(16,056)	(15,558)	48,167
Comprehensive income	$ 46,044	$ 31,366	$ 147,377	$ 179,411