Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 76,082	$ 64,540	$ 94,243
Unrealized gains (losses) on AFS securities arising during the period, net of taxes of $6,116, $(4,359), and $(3,468)	(19,077)	13,578	10,804
Unrealized gains on securities reclassified from held-to-maturity ("HTM") to AFS during the period, net of taxes of $0, $0, and $(750)	0	0	2,336
Changes in unrealized gains (losses) on cash flow hedges, net of taxes of $(6,153), $4,875, and $10,394	19,277	(15,184)	(32,379)
Comprehensive income	$ 76,282	$ 62,934	$ 75,004