Fair Value Measurements: Schedule of estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments, at cost	$ 3,000	$ 3,000	[1]
Recorded Amount
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	118,851	143,015
CDs held for investment	76,249	78,346
Investment securities	76,953	53,634
Investments in equity securities	953	958
FHLB stock	1,437	1,437
Other investments, at cost	3,000	3,000
Loans held for sale	5,420	6,071
Loans receivable, net	913,150	886,662
Accrued interest receivable	3,665	3,598
Certificates of deposits	165,408	165,655
Accrued interest payable	351	333
Fair Value
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	118,851	143,015
CDs held for investment	76,249	78,346
Investment securities	79,114	55,112
Investments in equity securities	953	958
FHLB stock	1,437	1,437
Other investments, at cost	3,000	3,000
Loans held for sale	5,501	6,260
Loans receivable, net	917,475	892,495
Accrued interest receivable	3,665	3,598
Certificates of deposits	166,432	166,852
Accrued interest payable	351	333
Fair Value | Fair Value, Inputs, Level 1
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	118,851	143,015
CDs held for investment	76,249	78,346
Investment securities	2,997	3,949
Investments in equity securities	953	958
FHLB stock	1,437	1,437
Other investments, at cost	3,000	3,000
Loans held for sale	5,501	6,260
Loans receivable, net	0	0
Accrued interest receivable	3,665	3,598
Certificates of deposits	0	0
Accrued interest payable	351	333
Fair Value | Fair Value, Inputs, Level 2
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
CDs held for investment	0	0
Investment securities	76,117	51,163
Investments in equity securities	0	0
FHLB stock	0	0
Other investments, at cost	0	0
Loans held for sale	0	0
Loans receivable, net	0	0
Accrued interest receivable	0	0
Certificates of deposits	0	0
Accrued interest payable	0	0
Fair Value | Fair Value, Inputs, Level 3
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
CDs held for investment	0	0
Investment securities	0	0
Investments in equity securities	0	0
FHLB stock	0	0
Other investments, at cost	0	0
Loans held for sale	0	0
Loans receivable, net	917,475	892,495
Accrued interest receivable	0	0
Certificates of deposits	166,432	166,852
Accrued interest payable	$ 0	$ 0

[1] Derived from audited consolidated financial statements.