Servicing Rights - Summary of Fair Values (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
SBA
Servicing Assets at Fair Value [Line Items]
Mortgage servicing rights (MSR), fair value	$ 115	$ 202
Mortgage servicing rights (MSR), average discount rates for estimating fair value	15.00%
Mortgage servicing rights (MSR), average conditional prepayment rates for estimating fair value	0.1629	0.1613
MSRs valuation allowances	$ 18	$ 8
Freddie Mac
Servicing Assets at Fair Value [Line Items]
Mortgage servicing rights (MSR), fair value	$ 3,120	$ 3,694	$ 4,171
Mortgage servicing rights (MSR), average discount rates for estimating fair value	9.00%	9.00%	8.99%
Mortgage servicing rights (MSR), average conditional prepayment rates for estimating fair value	0.1442	0.1131	0.0810