Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 64,540	$ 94,243	$ 98,927
Unrealized gains (losses) on AFS securities arising during the period, net of taxes of $(4,359), $(3,468), and $2,499	13,578	10,804	(6,741)
Unrealized gains on securities reclassified from held-to-maturity ("HTM") to AFS during the period, net of taxes of $0, $(750), and $0	0	2,336	0
Changes in unrealized gains (losses) on cash flow hedges, net of taxes of $4,875, $10,394, and $(2,785)	(15,184)	(32,379)	7,496
Comprehensive income	$ 62,934	$ 75,004	$ 99,682