Loans and Allowance for Loan Losses - Aging of Recorded Investment in Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Loans and Allowance for Loan Losses
Total Past Due	$ 9,269	$ 7,528
Current	1,141,532	1,104,146
Recorded investment in loans	1,150,801	1,111,674
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	1,988	2,471
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	712	539
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	6,569	4,518
Residential real estate [Member]
Loans and Allowance for Loan Losses
Total Past Due	2,402	3,804
Current	203,070	188,465
Recorded investment in loans	205,472	192,269
Residential real estate [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	1,716	1,693
Residential real estate [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	480
Residential real estate [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	686	1,631
Commercial real estate [Member]
Loans and Allowance for Loan Losses
Total Past Due	738	794
Current	140,796	141,343
Recorded investment in loans	141,534	142,137
Commercial real estate [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	88	109
Commercial real estate [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Commercial real estate [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	650	685
Single tenant net lease
Loans and Allowance for Loan Losses
Total Past Due		0
Current	373,143	335,600
Recorded investment in loans	373,143	335,600
Single tenant net lease | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Single tenant net lease | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Single tenant net lease | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due		0
SBA commercial real estate
Loans and Allowance for Loan Losses
Total Past Due	4,888	1,874
Current	54,222	55,103
Recorded investment in loans	59,110	56,977
SBA commercial real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
SBA commercial real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	469	0
SBA commercial real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	4,419	1,874
Multifamily
Loans and Allowance for Loan Losses
Total Past Due		0
Current	44,508	42,470
Recorded investment in loans	44,508	42,470
Multifamily | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Multifamily | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Multifamily | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due		0
Residential Construction
Loans and Allowance for Loan Losses
Total Past Due		0
Current	5,369	9,358
Recorded investment in loans	5,369	9,358
Residential Construction | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Residential Construction | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Residential Construction | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due		0
Commercial Construction
Loans and Allowance for Loan Losses
Total Past Due		0
Current	9,195	6,939
Recorded investment in loans	9,195	6,939
Commercial Construction | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Commercial Construction | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Commercial Construction | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due		0
Land and land development
Loans and Allowance for Loan Losses
Total Past Due	4	2
Current	10,906	9,410
Recorded investment in loans	10,910	9,412
Land and land development | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Land and land development | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Land and land development | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	4	2
Commercial Business
Loans and Allowance for Loan Losses
Total Past Due	157	63
Current	63,466	60,679
Recorded investment in loans	63,623	60,742
Commercial Business | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	120	63
Commercial Business | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
Commercial Business | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	37	0
SBA commercial business
Loans and Allowance for Loan Losses
Total Past Due	768	695
Current	181,230	204,347
Recorded investment in loans	181,998	205,042
SBA commercial business | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	373
SBA commercial business | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	0	0
SBA commercial business | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	768	322
Consumer
Loans and Allowance for Loan Losses
Total Past Due	312	296
Current	55,627	50,432
Recorded investment in loans	55,939	50,728
Consumer | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	64	233
Consumer | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	243	59
Consumer | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans and Allowance for Loan Losses
Total Past Due	$ 5	$ 4