Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ 5,400	$ 26,783	$ (691,944)	$ 117,080
Securities available for sale:
Net unrealized holding gain arising during the period	11,838	23,690	42,019	53,882
Reclassification adjustment for net (gain) loss realized in net income	0	(322)	0	191
Income tax expense	(2,919)	(5,761)	(10,359)	(13,329)
Net change in unrealized gain on securities available for sale	8,919	17,607	31,660	40,744
Total comprehensive income (loss)	$ 14,319	$ 44,390	$ (660,284)	$ 157,824