Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 4,276	$ 24,554	$ 26,787	$ 48,937
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on AFS securities arising during the period, net of taxes of $(3,332), $(982), $(3,187) and $(2,115)	10,378	3,061	9,926	6,588
Changes in unrealized gains (losses) on cash flow hedges, net of taxes of $7,200, $2,118, $5,459 and $5,246	(22,429)	(6,600)	(17,005)	(16,344)
Comprehensive (loss) income	$ (7,775)	$ 21,015	$ 19,708	$ 39,181