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	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 63		$ 172
Allowance for Loan Losses, Collectively Evaluated for Impairment	12,831		9,518
Allowance for Loan Losses, Total	12,894	$ 11,890	9,690	$ 9,631	$ 9,741	$ 9,530
Recorded Investment in Loans, Individually Evaluated for Impairment	5,891		5,937
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,026,485		893,213
Loans receivable	1,032,376		899,150
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	1,163		1,167
Allowance for Loan Losses, Total	1,163	1,149	1,167	1,118	1,154	1,086
Recorded Investment in Loans, Individually Evaluated for Impairment	1,410		1,192
Recorded Investment in Loans, Collectively Evaluated for Impairment	119,104		131,469
Loans receivable	120,514		132,661
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	665		481
Allowance for Loan Losses, Total	665	595	481	438	470	433
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	79,468		76,036
Loans receivable	79,468		76,036
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	6,719		4,154
Allowance for Loan Losses, Total	6,719	5,762	4,154	4,052	4,122	4,248
Recorded Investment in Loans, Individually Evaluated for Impairment	3,267		3,190
Recorded Investment in Loans, Collectively Evaluated for Impairment	452,187		415,927
Loans receivable	455,454		419,117
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	807		755
Allowance for Loan Losses, Total	807	697	755	702	666	671
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	73,011		75,411
Loans receivable	73,011		75,411
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	164		212
Allowance for Loan Losses, Total	164	204	212	221	249	178
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	7,412		10,779
Loans receivable	7,412		10,779
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	304		338
Allowance for Loan Losses, Total	304	423	338	384	384	563
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	19,793		24,051
Loans receivable	19,793		24,051
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	318		375
Allowance for Loan Losses, Total	318	394	375	367	272	135
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	14,430		19,256
Loans receivable	14,430		19,256
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	107		67
Allowance for Loan Losses, Total	107	80	67	126	244	49
Recorded Investment in Loans, Individually Evaluated for Impairment	0		0
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,161		1,803
Loans receivable	3,161		1,803
Mortgage loans, land
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	25		27
Allowance for Loan Losses, Collectively Evaluated for Impairment	617		670
Allowance for Loan Losses, Total	642	678	697	656	649	844
Recorded Investment in Loans, Individually Evaluated for Impairment	186		204
Recorded Investment in Loans, Collectively Evaluated for Impairment	26,823		30,566
Loans receivable	27,009		30,770
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	632		623
Allowance for Loan Losses, Total	632	656	623	645	667	649
Recorded Investment in Loans, Individually Evaluated for Impairment	586		603
Recorded Investment in Loans, Collectively Evaluated for Impairment	33,819		39,587
Loans receivable	34,405		40,190
Consumer loans, other
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0		17
Allowance for Loan Losses, Collectively Evaluated for Impairment	73		82
Allowance for Loan Losses, Total	73	78	99	87	112	117
Recorded Investment in Loans, Individually Evaluated for Impairment	10		23
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,542		4,289
Loans receivable	3,552		4,312
Commercial business loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	38		128
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,262		594
Allowance for Loan Losses, Total	1,300	$ 1,174	722	$ 835	$ 752	$ 557
Recorded Investment in Loans, Individually Evaluated for Impairment	432		725
Recorded Investment in Loans, Collectively Evaluated for Impairment	71,154		64,039
Loans receivable	71,586		$ 64,764
SBA PPP Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0
Allowance for Loan Losses, Collectively Evaluated for Impairment	0
Allowance for Loan Losses, Total	0
Recorded Investment in Loans, Individually Evaluated for Impairment	0
Recorded Investment in Loans, Collectively Evaluated for Impairment	122,581
Loans receivable	$ 122,581