Loans Receivable and Allowance for Loan Losses: Schedule of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	$ 13,703	$ 13,469	$ 13,414
Provision for (Recapture of) Loan Losses	2,132	270	0
Charge-offs	(19)	(59)	(3)
Recoveries	1	23	58
Allowance for loan losses, Ending Allowance	15,817	13,703	13,469
Mortgage loans, one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	1,658	1,154	1,163
Provision for (Recapture of) Loan Losses	759	504	(9)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	2,417	1,658	1,154
Mortgage loans, multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	855	765	718
Provision for (Recapture of) Loan Losses	301	90	47
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	1,156	855	765
Mortgage loans, commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	6,682	6,813	7,144
Provision for (Recapture of) Loan Losses	527	(131)	(331)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	7,209	6,682	6,813
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	675	644	832
Provision for (Recapture of) Loan Losses	75	31	(188)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	750	675	644
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	130	188	158
Provision for (Recapture of) Loan Losses	18	(58)	30
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	148	130	188
Mortgage loans, construction - commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	343	784	420
Provision for (Recapture of) Loan Losses	(27)	(441)	364
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	316	343	784
Mortgage loans, construction - multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	447	436	238
Provision for (Recapture of) Loan Losses	155	11	198
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	602	447	436
Mortgage loans - construction - land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	233	124	133
Provision for (Recapture of) Loan Losses	41	109	(9)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	274	233	124
Mortgage loans, land
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	397	470	572
Provision for (Recapture of) Loan Losses	9	(73)	(147)
Charge-offs	0	0	0
Recoveries	0	0	45
Allowance for loan losses, Ending Allowance	406	397	470
Consumer loans, home equity and second mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	440	528	593
Provision for (Recapture of) Loan Losses	79	(88)	(65)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	519	440	528
Consumer loans, other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	42	50	71
Provision for (Recapture of) Loan Losses	14	1	(24)
Charge-offs	(4)	(10)	(1)
Recoveries	1	1	4
Allowance for loan losses, Ending Allowance	53	42	50
Commercial business loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	1,801	1,513	1,372
Provision for (Recapture of) Loan Losses	181	315	134
Charge-offs	(15)	(49)	(2)
Recoveries	0	22	9
Allowance for loan losses, Ending Allowance	$ 1,967	$ 1,801	$ 1,513

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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