FDIC Indemnification Asset - Summary of FDIC Indemnification Asset Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
FDIC Indemnification Asset [Roll Forward]
Balance, beginning of period	$ 832	$ 1,950	$ 1,079	$ 2,502
Amortization	(390)	(360)	(641)	(853)
Changes in expected reimbursements from FDIC for changes in expected credit losses	0	(13)	0	(13)
Changes in reimbursable expenses	0	(16)	0	(41)
Payments (reimbursements) of covered losses to (from) the FDIC	39	(9)	43	(43)
Balance, end of period	$ 481	$ 1,552	$ 481	$ 1,552