Loans Receivable and Allowance for Loan Losses: Past Due Status of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2022		Sep. 30, 2021
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	$ 1,150,450		$ 987,066
Loans receivable, Non-Accrual	2,059	[1]	2,854	[2]
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	37		5
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		180
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	2,096		3,039
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1,148,354		984,027
Mortgage loans, one-to-four family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	176,116		119,935
Loans receivable, Non-Accrual	388	[1]	407	[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		180
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	388		587
Mortgage loans, one-to-four family | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	175,728		119,348
Mortgage loans, multi-family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	95,025		87,563
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	95,025		87,563
Mortgage loans, commercial
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	536,650		470,650
Loans receivable, Non-Accrual	657	[1]	773	[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	657		773
Mortgage loans, commercial | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	535,993		469,877
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	67,091		61,003
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	0		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	0		0
Mortgage loans, construction - custom and owner/builder | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	67,091		61,003
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	8,364		9,657
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	8,364		9,657
Mortgage loans, construction - commercial
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	29,059		38,931
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	29,059		38,931
Mortgage loans, construction - multi-family
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	34,354		22,888
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	34,354		22,888
Mortgage loans - construction - land development
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	13,582		5,502
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	13,582		5,502
Mortgage loans, land
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	26,854		19,936
Loans receivable, Non-Accrual	450	[1]	683	[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	450		683
Mortgage loans, land | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	26,404		19,253
Consumer loans, home equity and second mortgage
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	35,187		32,988
Loans receivable, Non-Accrual	252	[1]	516	[2]
Consumer loans, home equity and second mortgage | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	37		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 | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	289		516
Consumer loans, home equity and second mortgage | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	34,898		32,472
Consumer loans, other
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	2,128		2,512
Loans receivable, Non-Accrual	3	[1]	17	[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	3		17
Consumer loans, other | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	2,125		2,495
Commercial business loans
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	125,039		74,579
Loans receivable, Non-Accrual	309	[1]	458	[2]
Commercial business loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	0		5
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	309		463
Commercial business loans | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	124,730		74,116
SBA PPP Loans
Financing Receivable, Past Due [Line Items]
Loans receivable, Total Past Due	1,001		40,922
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	$ 1,001		$ 40,922

[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.