Loans Receivable and Allowance for Loan Losses: Past Due Status of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2023		Sep. 30, 2022
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	$ 1,323,364		$ 1,150,450
Loans receivable, Non-Accrual	1,514	[1]	2,059	[2]
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	151		37
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		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
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1,665		2,096
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1,321,699		1,148,354
Mortgage loans, one-to-four family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	253,227		176,116
Loans receivable, Non-Accrual	368	[1]	388	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	368		388
Mortgage loans, one-to-four family | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	252,859		175,728
Mortgage loans, multi-family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	127,176		95,025
Loans receivable, Non-Accrual	0	[1]	0	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
Mortgage loans, multi-family | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	127,176		95,025
Mortgage loans, commercial
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	568,265		536,650
Loans receivable, Non-Accrual	683	[1]	657	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	683		657
Mortgage loans, commercial | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	567,582		535,993
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	73,239		67,091
Loans receivable, Non-Accrual	0	[1]	0	[2]
Mortgage loans, construction - custom and owner/builder | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	151		0
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	151		0
Mortgage loans, construction - custom and owner/builder | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	73,088		67,091
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	9,361		8,364
Loans receivable, Non-Accrual	0	[1]	0	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
Mortgage loans, construction - speculative one-to-four family | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	9,361		8,364
Mortgage loans, construction - commercial
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	26,030		29,059
Loans receivable, Non-Accrual	0	[1]	0	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
Mortgage loans, construction - commercial | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	26,030		29,059
Mortgage loans, construction - multi-family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	45,890		34,354
Loans receivable, Non-Accrual	0	[1]	0	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
Mortgage loans, construction - multi-family | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	45,890		34,354
Mortgage loans - construction - land development
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	16,129		13,582
Loans receivable, Non-Accrual	0	[1]	0	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
Mortgage loans - construction - land development | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	16,129		13,582
Mortgage loans, land
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	26,726		26,854
Loans receivable, Non-Accrual	0	[1]	450	[2]
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		450
Mortgage loans, land | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	26,726		26,404
Consumer loans, home equity and second mortgage
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	38,281		35,187
Loans receivable, Non-Accrual	177	[1]	252	[2]
Consumer loans, home equity and second mortgage | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		37
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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	177		289
Consumer loans, home equity and second mortgage | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	38,104		34,898
Consumer loans, other
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	2,772		2,128
Loans receivable, Non-Accrual	0	[1]	3	[2]
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	0		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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		3
Consumer loans, other | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	2,772		2,125
Commercial business loans
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	135,802		125,039
Loans receivable, Non-Accrual	286	[1]	309	[2]
Commercial business loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
Commercial business loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	286		309
Commercial business loans | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	135,516		124,730
SBA PPP Loans
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	466		1,001
Loans receivable, Non-Accrual	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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		0
SBA PPP Loans | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	$ 466		$ 1,001

[1] Includes non-accrual loans past due 90 days or more and other loans classified as non-accrual.

[2] Includes non-accrual loans past due 90 days or more and other loans classified as non-accrual.