Loans Receivable and Allowance for Loan Losses: Schedule of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	$ 9,530	$ 9,553	$ 9,826
Provision for (Recapture of) Loan Losses	0	0	(1,250)
Charge-offs	(161)	(56)	(133)
Recoveries	321	33	1,110
Allowance for loan losses, Ending Allowance	9,690	9,530	9,553
Mortgage loans, one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	1,086	1,082	1,239
Provision for (Recapture of) Loan Losses	(23)	4	(178)
Charge-offs	0	0	0
Recoveries	104	0	21
Allowance for loan losses, Ending Allowance	1,167	1,086	1,082
Mortgage loans, multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	433	447	473
Provision for (Recapture of) Loan Losses	48	(14)	(26)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	481	433	447
Mortgage loans, commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	4,248	4,184	4,384
Provision for (Recapture of) Loan Losses	(260)	92	(1,248)
Charge-offs	0	(28)	(13)
Recoveries	166	0	1,061
Allowance for loan losses, Ending Allowance	4,154	4,248	4,184
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	671	699	619
Provision for (Recapture of) Loan Losses	82	(28)	80
Charge-offs	0	0	0
Recoveries	2	0	0
Allowance for loan losses, Ending Allowance	755	671	699
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	178	128	130
Provision for (Recapture of) Loan Losses	34	37	(8)
Charge-offs	0	0	0
Recoveries	0	13	6
Allowance for loan losses, Ending Allowance	212	178	128
Mortgage loans, construction - commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	563	303	268
Provision for (Recapture of) Loan Losses	(225)	260	35
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	338	563	303
Mortgage loans, construction - multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	135	173	316
Provision for (Recapture of) Loan Losses	240	(38)	(143)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	375	135	173
Mortgage loans - construction - land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	49	0
Provision for (Recapture of) Loan Losses	18	49
Charge-offs	0	0
Recoveries	0	0
Allowance for loan losses, Ending Allowance	67	49	0
Mortgage loans, land
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	844	918	820
Provision for (Recapture of) Loan Losses	(116)	(71)	189
Charge-offs	(49)	(22)	(110)
Recoveries	18	19	19
Allowance for loan losses, Ending Allowance	697	844	918
Consumer loans, home equity and second mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	649	983	939
Provision for (Recapture of) Loan Losses	(21)	(334)	44
Charge-offs	(5)	0	0
Recoveries	0	0	0
Allowance for loan losses, Ending Allowance	623	649	983
Consumer loans, other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	117	121	156
Provision for (Recapture of) Loan Losses	(19)	1	(28)
Charge-offs	(5)	(6)	(10)
Recoveries	6	1	3
Allowance for loan losses, Ending Allowance	99	117	121
Commercial business loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Allowance	557	515	482
Provision for (Recapture of) Loan Losses	242	42	33
Charge-offs	(102)	0	0
Recoveries	25	0	0
Allowance for loan losses, Ending Allowance	$ 722	$ 557	$ 515

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 recovery of financing receivables doubtful of collection that were previously charged off.

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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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