Loans Receivable and Allowance for Loan Losses: Schedule of loans evaluated individually for impairment and collectively evaluated for impairment in the allowance for loan losses (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 127	$ 247
Allowance for Loan Losses, Collectively Evaluated for Impairment	13,576	13,222
Allowance for Loan Losses, Total	13,703	13,469	$ 13,414	$ 9,690
Recorded Investment in Loans, Individually Evaluated for Impairment	4,532	5,224
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,145,918	981,842
Loans receivable	1,150,450	987,066
Mortgage loans, one-to-four family
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,658	1,154
Allowance for Loan Losses, Total	1,658	1,154	1,163	1,167
Recorded Investment in Loans, Individually Evaluated for Impairment	388	407
Recorded Investment in Loans, Collectively Evaluated for Impairment	175,728	119,528
Loans receivable	176,116	119,935
Mortgage loans, multi-family
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	855	765
Allowance for Loan Losses, Total	855	765	718	481
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	95,025	87,563
Loans receivable	95,025	87,563
Mortgage loans, commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	6,682	6,813
Allowance for Loan Losses, Total	6,682	6,813	7,144	4,154
Recorded Investment in Loans, Individually Evaluated for Impairment	2,988	3,143
Recorded Investment in Loans, Collectively Evaluated for Impairment	533,662	467,507
Loans receivable	536,650	470,650
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	675	644
Allowance for Loan Losses, Total	675	644	832	755
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	67,091	61,003
Loans receivable	67,091	61,003
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	130	188
Allowance for Loan Losses, Total	130	188	158	212
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	8,364	9,657
Loans receivable	8,364	9,657
Mortgage loans, construction - commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	343	784
Allowance for Loan Losses, Total	343	784	420	338
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	29,059	38,931
Loans receivable	29,059	38,931
Mortgage loans, construction - multi-family
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	447	436
Allowance for Loan Losses, Total	447	436	238	375
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	34,354	22,888
Loans receivable	34,354	22,888
Mortgage loans - construction - land development
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	233	124
Allowance for Loan Losses, Total	233	124	133	67
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	13,582	5,502
Loans receivable	13,582	5,502
Mortgage loans, land
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	76
Allowance for Loan Losses, Collectively Evaluated for Impairment	397	394
Allowance for Loan Losses, Total	397	470	572	697
Recorded Investment in Loans, Individually Evaluated for Impairment	450	683
Recorded Investment in Loans, Collectively Evaluated for Impairment	26,404	19,253
Loans receivable	26,854	19,936
Consumer loans, home equity and second mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	440	528
Allowance for Loan Losses, Total	440	528	593	623
Recorded Investment in Loans, Individually Evaluated for Impairment	394	516
Recorded Investment in Loans, Collectively Evaluated for Impairment	34,793	32,472
Loans receivable	35,187	32,988
Consumer loans, other
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	42	50
Allowance for Loan Losses, Total	42	50	71	99
Recorded Investment in Loans, Individually Evaluated for Impairment	3	17
Recorded Investment in Loans, Collectively Evaluated for Impairment	2,125	2,495
Loans receivable	2,128	2,512
Commercial business loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	127	171
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,674	1,342
Allowance for Loan Losses, Total	1,801	1,513	$ 1,372	$ 722
Recorded Investment in Loans, Individually Evaluated for Impairment	309	458
Recorded Investment in Loans, Collectively Evaluated for Impairment	124,730	74,121
Loans receivable	125,039	74,579
SBA PPP Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	0	0
Allowance for Loan Losses, Total	0	0
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,001	40,922
Loans receivable	$ 1,001	$ 40,922