Loan Servicing Rights - Summary of Fair Values (Details) - Freddie Mac - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Servicing Assets at Fair Value [Line Items]
Mortgage servicing rights (MSR), fair value	$ 4,634	$ 4,655	$ 5,469
Mortgage servicing rights (MSR), average discount rates for estimating fair value	9.00%	10.00%	9.50%
Mortgage servicing rights (MSR), average conditional prepayment rates for estimating fair value	0.0737	0.0703	0.0623