Fair Value Measurements: Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in equity securities	$ 955	$ 977
Recorded Amount
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	580,196	314,452
CDs held for investment	28,482	65,545
Investment securities	132,278	85,797
Investments in equity securities	955	977
FHLB stock	2,103	1,922
Other investments	3,000	3,000
Loans held for sale	3,217	4,509
Loans receivable, net	968,454	1,013,875
Accrued interest receivable	3,745	4,484
Certificates of deposit	134,129	158,524
Accrued interest payable	134	274
Fair Value
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	580,196	314,452
CDs held for investment	28,482	65,545
Investment securities	133,286	87,734
Investments in equity securities	955	977
FHLB stock	2,103	1,922
Other investments	3,000	3,000
Loans held for sale	3,290	4,664
Loans receivable, net	981,905	1,034,876
Accrued interest receivable	3,745	4,484
Certificates of deposit	135,178	160,921
Accrued interest payable	134	274
Fair Value \| Fair Value, Inputs, Level 1
Fair value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	580,196	314,452
CDs held for investment	28,482	65,545
Investment securities	28,670	0
Investments in equity securities	955	977
FHLB stock	2,103	1,922
Other investments	3,000	3,000
Loans held for sale	3,290	4,664
Loans receivable, net	0	0
Accrued interest receivable	3,745	4,484
Certificates of deposit	0	0
Accrued interest payable	134	274
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	104,616	87,235
Investments in equity securities	0	0
FHLB stock	0	0
Other investments	0	0
Loans held for sale	0	0
Loans receivable, net	0	0
Accrued interest receivable	0	0
Certificates of deposit	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	499
Investments in equity securities	0	0
FHLB stock	0	0
Other investments	0	0
Loans held for sale	0	0
Loans receivable, net	981,905	1,034,876
Accrued interest receivable	0	0
Certificates of deposit	135,178	160,921
Accrued interest payable	$ 0	$ 0

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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-Publisher FASB
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-SubTopic 320
-Section 45
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- Definition

Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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- Definition

Amount of investments classified as other.

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-Topic 944
-SubTopic 210
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