FDIC Indemnification Asset - Summary of FDIC Indemnification Asset Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
FDIC Indemnification Asset [Roll Forward]
Balance, beginning of period	$ 481	$ 1,552	$ 1,079	$ 2,502
Amortization	(371)	(301)	(1,012)	(1,154)
Changes in expected reimbursements from FDIC for changes in expected credit losses	0	2	0	(11)
Changes in reimbursable expenses	0	0	0	(41)
Payments (reimbursements) of covered losses to (from) the FDIC	3	17	46	(26)
Balance, end of period	$ 113	$ 1,270	$ 113	$ 1,270