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, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 476	$ 776
Allowance for Loan Losses, Collectively Evaluated for Impairment	9,077	9,050
Allowance for Loan Losses, Total	9,553	9,826	$ 9,924	$ 10,427
Recorded Investment in Loans, Individually Evaluated for Impairment	6,992	16,237
Recorded Investment in Loans, Collectively Evaluated for Impairment	695,391	658,964
Loans receivable	702,383	675,201
Mortgage loans, one-to-four family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	70
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,082	1,169
Allowance for Loan Losses, Total	1,082	1,239	1,480	1,650
Recorded Investment in Loans, Individually Evaluated for Impairment	1,443	2,264
Recorded Investment in Loans, Collectively Evaluated for Impairment	116,704	116,296
Loans receivable	118,147	118,560
Mortgage loans, multi-family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	447	473
Allowance for Loan Losses, Total	447	473	392	387
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	58,607	62,303
Loans receivable	58,607	62,303
Mortgage loans, commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	26	413
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,158	3,971
Allowance for Loan Losses, Total	4,184	4,384	4,065	4,836
Recorded Investment in Loans, Individually Evaluated for Impairment	3,873	11,309
Recorded Investment in Loans, Collectively Evaluated for Impairment	325,054	301,216
Loans receivable	328,927	312,525
Mortgage loans, construction - custom and owner/builder
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	699	619
Allowance for Loan Losses, Total	699	619	451	450
Recorded Investment in Loans, Individually Evaluated for Impairment	0	367
Recorded Investment in Loans, Collectively Evaluated for Impairment	63,538	51,662
Loans receivable	63,538	52,029
Mortgage loans, construction - speculative one-to-four family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	128	130
Allowance for Loan Losses, Total	128	130	123	52
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	4,639	4,074
Loans receivable	4,639	4,074
Mortgage loans, construction - commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	303	268
Allowance for Loan Losses, Total	303	268	426	78
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	11,016	6,841
Loans receivable	11,016	6,841
Mortgage loans, construction - multi-family
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	173	316
Allowance for Loan Losses, Total	173	316	283	25
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	6,912	11,539
Loans receivable	6,912	11,539
Mortgage loans, land
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	125	53
Allowance for Loan Losses, Collectively Evaluated for Impairment	793	767
Allowance for Loan Losses, Total	918	820	1,021	1,434
Recorded Investment in Loans, Individually Evaluated for Impairment	1,119	1,268
Recorded Investment in Loans, Collectively Evaluated for Impairment	22,791	20,359
Loans receivable	23,910	21,627
Consumer loans, home equity and second mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	325	227
Allowance for Loan Losses, Collectively Evaluated for Impairment	658	712
Allowance for Loan Losses, Total	983	939	1,073	879
Recorded Investment in Loans, Individually Evaluated for Impairment	557	999
Recorded Investment in Loans, Collectively Evaluated for Impairment	37,863	38,728
Loans receivable	38,420	39,727
Consumer loans, other
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	13
Allowance for Loan Losses, Collectively Evaluated for Impairment	121	143
Allowance for Loan Losses, Total	121	156	187	176
Recorded Investment in Loans, Individually Evaluated for Impairment	0	30
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,823	4,109
Loans receivable	3,823	4,139
Commercial business loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	515	482
Allowance for Loan Losses, Total	515	482	$ 423	$ 460
Recorded Investment in Loans, Individually Evaluated for Impairment	0	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	44,444	41,837
Loans receivable	$ 44,444	$ 41,837