Loans and Allowance for Credit Losses - Aging of recorded investment in past due loans (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Loans and Allowance for Loan Losses
Total loans	$ 1,900,918	$ 1,900,918
Total loans		1,786,194
30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	3,857	3,921
60 to 89 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	1,450	199
90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	7,989	6,499
Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	13,296	10,619
Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	1,887,622	1,775,575
Residential real estate
Loans and Allowance for Loan Losses
Total loans	609,182	609,182
Total loans		528,410
Residential real estate | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	2,764	2,715
Residential real estate | 60 to 89 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	1,398	132
Residential real estate | 90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	2,304	1,818
Residential real estate | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	6,466	4,665
Residential real estate | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	602,716	523,745
Commercial real estate
Loans and Allowance for Loan Losses
Total loans	183,522	183,522
Total loans		187,232
Commercial real estate | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	254	23
Commercial real estate | 60 to 89 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment		62
Commercial real estate | 90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	496
Commercial real estate | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	750	85
Commercial real estate | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	182,772	187,147
Single tenant net lease
Loans and Allowance for Loan Losses
Total loans	751,357	751,357
Total loans		757,388
Single tenant net lease | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	751,357	757,388
SBA commercial real estate
Loans and Allowance for Loan Losses
Total loans	47,008	47,008
Total loans		47,078
SBA commercial real estate | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	359	764
SBA commercial real estate | 60 to 89 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	49
SBA commercial real estate | 90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	4,422	3,877
SBA commercial real estate | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	4,830	4,641
SBA commercial real estate | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	42,178	42,437
Multifamily
Loans and Allowance for Loan Losses
Total loans	39,944	39,944
Total loans		34,892
Multifamily | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	39,944	34,892
Residential construction
Loans and Allowance for Loan Losses
Total loans	52,166	52,166
Total loans		24,924
Residential construction | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	52,166	24,924
Commercial construction
Loans and Allowance for Loan Losses
Total loans	20,978	20,978
Total loans		14,588
Commercial construction | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	20,978	14,588
Land and land development
Loans and Allowance for Loan Losses
Total loans	15,573	15,573
Total loans		17,234
Land and land development | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	63	40
Land and land development | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	63	40
Land and land development | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	15,510	17,194
Commercial business
Loans and Allowance for Loan Losses
Total loans	124,153	124,153
Total loans		117,594
Commercial business | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	14	112
Commercial business | 90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	37	86
Commercial business | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	51	198
Commercial business | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	124,102	117,396
SBA commercial business
Loans and Allowance for Loan Losses
Total loans	18,568	18,568
Total loans		16,939
SBA commercial business | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	213	130
SBA commercial business | 90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	718	682
SBA commercial business | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	931	812
SBA commercial business | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	17,637	16,127
Consumer
Loans and Allowance for Loan Losses
Total loans	38,467	38,467
Total loans		39,915
Consumer | 30 to 59 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	190	137
Consumer | 60 to 89 Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	3	5
Consumer | 90+ Days Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	12	36
Consumer | Total Past Due
Loans and Allowance for Loan Losses
Financing receivable recorded investment	205	178
Consumer | Current
Loans and Allowance for Loan Losses
Financing receivable recorded investment	$ 38,262	$ 39,737