CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 65,934	$ 49,359	$ 145,443	$ 99,640
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) during the period on available-for-sale investment securities, net of tax	18,993	(33,767)	13,471	(46,701)
Reclassification adjustment of net (gain) loss from sale of available-for-sale securities included in net income, net of tax	0	0	0	62
Net unrealized gain (loss) from investment securities, net of reclassification adjustment	18,993	(33,767)	13,471	(46,639)
Net unrealized gain (loss) during the period on borrowings cash flow hedges, net of tax	(16,897)	43,369	(22,130)	48,332
Net unrealized gain (loss) in cash flow hedging instruments, net of reclassification adjustment	(16,897)	43,369	(22,130)	48,332
Other comprehensive income (loss)	2,096	9,602	(8,659)	1,693
Comprehensive income	$ 68,030	$ 58,961	$ 136,784	$ 101,333