Loans Receivable and Allowance for Loan Losses: Past Due Status of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	$ 1,444,426	$ 1,323,364
Non-accrual loans	3,885	1,514
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	424	151
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	170	0
Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	4,479	1,665
Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1,439,947	1,321,699
Mortgage loans, one-to-four family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	299,123	253,227
Non-accrual loans	49	368
Mortgage loans, one-to-four family | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, one-to-four family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, one-to-four family | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, one-to-four family | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	49	368
Mortgage loans, one-to-four family | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	299,074	252,859
Mortgage loans, multi-family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	177,350	127,176
Non-accrual loans	0	0
Mortgage loans, multi-family | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, multi-family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, multi-family | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, multi-family | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, multi-family | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	177,350	127,176
Mortgage loans, commercial
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	599,219	568,265
Non-accrual loans	1,158	683
Mortgage loans, commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, commercial | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1,158	683
Mortgage loans, commercial | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	598,061	567,582
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	81,274	73,239
Non-accrual loans	0	0
Mortgage loans, construction - custom and owner/builder | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	151
Mortgage loans, construction - custom and owner/builder | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - custom and owner/builder | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, construction - custom and owner/builder | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	151
Mortgage loans, construction - custom and owner/builder | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	81,274	73,088
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	7,451	9,361
Non-accrual loans	0	0
Mortgage loans, construction - speculative one-to-four family | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - speculative one-to-four family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - speculative one-to-four family | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, construction - speculative one-to-four family | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - speculative one-to-four family | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	7,451	9,361
Mortgage loans, construction - commercial
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	23,812	26,030
Non-accrual loans	0	0
Mortgage loans, construction - commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - commercial | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, construction - commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - commercial | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	23,812	26,030
Mortgage loans, construction - multi-family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	20,757	45,890
Non-accrual loans	0	0
Mortgage loans, construction - multi-family | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - multi-family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - multi-family | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, construction - multi-family | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, construction - multi-family | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	20,757	45,890
Mortgage loans - construction - land development
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	16,029	16,129
Non-accrual loans	0	0
Mortgage loans - construction - land development | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans - construction - land development | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans - construction - land development | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans - construction - land development | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans - construction - land development | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	16,029	16,129
Mortgage loans, land
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	29,366	26,726
Non-accrual loans	0	0
Mortgage loans, land | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, land | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, land | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Mortgage loans, land | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Mortgage loans, land | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	29,366	26,726
Consumer loans, home equity and second mortgage
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	47,913	38,281
Non-accrual loans	618	177
Consumer loans, home equity and second mortgage | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Consumer loans, home equity and second mortgage | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Consumer loans, home equity and second mortgage | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Consumer loans, home equity and second mortgage | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	618	177
Consumer loans, home equity and second mortgage | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	47,295	38,104
Consumer loans, other
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	3,129	2,772
Non-accrual loans	0	0
Consumer loans, other | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
Consumer loans, other | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1	0
Consumer loans, other | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Consumer loans, other | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1	0
Consumer loans, other | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	3,128	2,772
Commercial business loans
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	138,743	135,802
Non-accrual loans	2,060	286
Commercial business loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	424	0
Commercial business loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	169	0
Commercial business loans | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
Commercial business loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	2,653	286
Commercial business loans | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	136,090	135,516
SBA PPP Loans
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	260	466
Non-accrual loans	0	0
SBA PPP Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
SBA PPP Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
SBA PPP Loans | Past Due 90 Days or More and Still Accruing
Financing Receivable, Past Due [Line Items]
Past Due 90 Days or More and Still Accruing	0	0
SBA PPP Loans | Total Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0	0
SBA PPP Loans | Current
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	$ 260	$ 466