Loans Receivable and Allowance for Loan Losses: Financing Receivable Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	$ 1,323,364	$ 1,150,450
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	1,299,220	1,132,403
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	17,758	10,423
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	237
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	6,386	7,387
Mortgage loans, one-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	253,227	176,116
Mortgage loans, one-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	252,859	175,687
Mortgage loans, one-to-four family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	38
Mortgage loans, one-to-four family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, one-to-four family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	368	391
Mortgage loans, multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	127,176	95,025
Mortgage loans, multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	127,176	95,025
Mortgage loans, multi-family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, multi-family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, multi-family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	568,265	536,650
Mortgage loans, commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	551,669	522,741
Mortgage loans, commercial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	11,143	7,940
Mortgage loans, commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	237
Mortgage loans, commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	5,453	5,732
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	73,239	67,091
Mortgage loans, construction - custom and owner/builder | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	68,181	65,249
Mortgage loans, construction - custom and owner/builder | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	5,058	1,842
Mortgage loans, construction - custom and owner/builder | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - custom and owner/builder | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	9,361	8,364
Mortgage loans, construction - speculative one-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	9,361	8,364
Mortgage loans, construction - speculative one-to-four family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - speculative one-to-four family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - speculative one-to-four family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	26,030	29,059
Mortgage loans, construction - commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	25,063	29,059
Mortgage loans, construction - commercial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	967	0
Mortgage loans, construction - commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	45,890	34,354
Mortgage loans, construction - multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	45,890	34,354
Mortgage loans, construction - multi-family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - multi-family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - multi-family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans - construction - land development
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	16,129	13,582
Mortgage loans - construction - land development | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	16,129	13,557
Mortgage loans - construction - land development | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans - construction - land development | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans - construction - land development | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	25
Mortgage loans, land
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	26,726	26,854
Mortgage loans, land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	26,226	25,882
Mortgage loans, land | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	500	522
Mortgage loans, land | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, land | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	450
Consumer loans, home equity and second mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	38,281	35,187
Consumer loans, home equity and second mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	37,982	34,709
Consumer loans, home equity and second mortgage | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	34	19
Consumer loans, home equity and second mortgage | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Consumer loans, home equity and second mortgage | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	265	459
Consumer loans, other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	2,772	2,128
Consumer loans, other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	2,716	2,063
Consumer loans, other | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	56	62
Consumer loans, other | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Consumer loans, other | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	3
Commercial business loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	135,802	125,039
Commercial business loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	135,502	124,712
Commercial business loans | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Commercial business loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Commercial business loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	300	327
SBA PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	466	1,001
SBA PPP Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	466	1,001
SBA PPP Loans | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
SBA PPP Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
SBA PPP Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	$ 0	$ 0