Summary of Significant Accounting Policies - Changes from ASU Adoption (Details) - USD ($)	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Assets
ACL on investment securities	$ 60,000	$ 0
ACL on loans	17,478,000	15,817,000
Net deferred tax asset		(26,000)
Liabilities
ACL on unfunded commitments	327,000	332,000
Total equity:	$ 245,413,000	233,073,000	$ 218,569,000	$ 206,899,000
Impact of Adopting CECL (ASU 2016-13)
Assets
ACL on investment securities		92,000
ACL on loans		461,000
Net deferred tax asset		130,000
Liabilities
ACL on unfunded commitments		65,000
Total equity:		(488,000)
As Reported Under ASU 2016-13
Assets
ACL on investment securities		92,000
ACL on loans		16,278,000
Net deferred tax asset		104,000
Liabilities
ACL on unfunded commitments		397,000
Total equity:		$ 232,585,000