FDIC Indemnification Asset - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
FDIC Indemnification Asset [Roll Forward]
Balance, beginning of period	$ 1,079	$ 2,502	$ 5,704
Amortization	(1,012)	(1,386)	(2,778)
Changes in expected reimbursements from FDIC for changes in expected credit losses	0	(10)	(122)
Changes in reimbursable expenses	0	(41)	(1,072)
Payments of covered losses to the FDIC	47	14	770
Settlement upon expiration of loss-sharing arrangement	(114)	0	0
Balance, end of period	$ 0	$ 1,079	$ 2,502