Loans Receivable and Allowance for Loan Losses: Schedule of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	$ 13,414	$ 9,690	$ 9,530
Provision for (Recapture of) Loan Losses	0	3,700	0
Charge-offs	(3)	(27)	(161)
Recoveries	58	51	321
Allowance for loan losses, Ending Allowance	13,469	13,414	9,690
Mortgage loans, one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	1,163	1,167	1,086
Provision for (Recapture of) Loan Losses	(9)	(6)	(23)
Charge-offs	0	0	0
Recoveries	0	2	104
Allowance for loan losses, Ending Allowance	1,154	1,163	1,167
Mortgage loans, multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	718	481	433
Provision for (Recapture of) Loan Losses	47	237	48
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	765	718	481
Mortgage loans, commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	7,144	4,154	4,248
Provision for (Recapture of) Loan Losses	(331)	2,984	(260)
Charge-offs	0	0	0
Recoveries	0	6	166
Allowance for loan losses, Ending Allowance	6,813	7,144	4,154
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	832	755	671
Provision for (Recapture of) Loan Losses	(188)	72	82
Charge-offs	0	0	0
Recoveries	0	5	2
Allowance for loan losses, Ending Allowance	644	832	755
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	158	212	178
Provision for (Recapture of) Loan Losses	30	(54)	34
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	188	158	212
Mortgage loans, construction - commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	420	338	563
Provision for (Recapture of) Loan Losses	364	82	(225)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	784	420	338
Mortgage loans, construction - multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	238	375	135
Provision for (Recapture of) Loan Losses	198	(137)	240
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	436	238	375
Mortgage loans - construction - land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	133	67	49
Provision for (Recapture of) Loan Losses	(9)	66	18
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	124	133	67
Mortgage loans, land
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	572	697	844
Provision for (Recapture of) Loan Losses	(147)	(145)	(116)
Charge-offs	0	0	(49)
Recoveries	45	20	18
Allowance for loan losses, Ending Allowance	470	572	697
Consumer loans, home equity and second mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	593	623	649
Provision for (Recapture of) Loan Losses	(65)	(45)	(21)
Charge-offs	0	0	(5)
Recoveries	0	15	0
Allowance for loan losses, Ending Allowance	528	593	623
Consumer loans, other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	71	99	117
Provision for (Recapture of) Loan Losses	(24)	(19)	(19)
Charge-offs	(1)	(12)	(5)
Recoveries	4	3	6
Allowance for loan losses, Ending Allowance	50	71	99
Commercial business loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	1,372	722	557
Provision for (Recapture of) Loan Losses	134	665	242
Charge-offs	(2)	(15)	(102)
Recoveries	9	0	25
Allowance for loan losses, Ending Allowance	$ 1,513	$ 1,372	$ 722

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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