Loans Receivable and Allowance for Loan Losses: Financing Receivable Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	$ 1,150,450	$ 987,066
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	1,132,403	965,950
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	10,423	12,500
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	237	5,012
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	7,387	3,604
Mortgage loans, one-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	176,116	119,935
Mortgage loans, one-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	175,687	118,857
Mortgage loans, one-to-four family | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	38	129
Mortgage loans, one-to-four family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	537
Mortgage loans, one-to-four family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	391	412
Mortgage loans, multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	95,025	87,563
Mortgage loans, multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	95,025	87,563
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	536,650	470,650
Mortgage loans, commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	522,741	456,188
Mortgage loans, commercial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	7,940	10,285
Mortgage loans, commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	237	2,921
Mortgage loans, commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	5,732	1,256
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	67,091	61,003
Mortgage loans, construction - custom and owner/builder | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	65,249	59,699
Mortgage loans, construction - custom and owner/builder | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	1,842	1,304
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	8,364	9,657
Mortgage loans, construction - speculative one-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	8,364	9,657
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	29,059	38,931
Mortgage loans, construction - commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	29,059	37,414
Mortgage loans, construction - commercial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	0
Mortgage loans, construction - commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	1,517
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	34,354	22,888
Mortgage loans, construction - multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	34,354	22,888
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	13,582	5,502
Mortgage loans - construction - land development | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	13,557	5,467
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	25	35
Mortgage loans, land
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	26,854	19,936
Mortgage loans, land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	25,882	18,648
Mortgage loans, land | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	522	558
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	450	730
Consumer loans, home equity and second mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	35,187	32,988
Consumer loans, home equity and second mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	34,709	32,190
Consumer loans, home equity and second mortgage | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	19	145
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	459	653
Consumer loans, other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	2,128	2,512
Consumer loans, other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	2,063	2,465
Consumer loans, other | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	62	30
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	3	17
Commercial business loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	125,039	74,579
Commercial business loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	124,712	73,992
Commercial business loans | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	49
Commercial business loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	0	37
Commercial business loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	327	501
SBA PPP Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	1,001	40,922
SBA PPP Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable	1,001	40,922
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