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Employee Stock Ownership and 401(k) Plan: Narrative (Details) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 1998 USD ($) shares | Sep. 30, 2023 USD ($) component shares | Sep. 30, 2022 USD ($) shares | Sep. 30, 2021 USD ($) shares
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |  |
ESOP shares (in shares) | shares |  | 317,094 | 372,559 | 397,626
401(k) |  |  |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |  |
401(k), employer safe harbor contribution (as a percent) |  | 3.00% |  |
401(k), employer contributions | $ |  | $ 1,039,000 | $ 942,000 | $ 931,000
KSOP |  |  |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |  |
Number of components in KSOP | component |  | 2 |  |
Required service period (in years) |  | 1 year |  |
Employee minimum age requirement (in years) |  | 18 years |  |
Award vesting period (in years) |  | 6 years |  |
ESOP |  |  |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |  |
ESOP, loan borrowed from employer | $ | $ 7,930,000 |  |  |
ESOP, shares purchased for plan (in shares) | shares | 1,058,000 |  |  |
ESOP, shares distributed to participants (in shares) | shares |  | 740,906 |  |
Earned ESOP shares | $ |  | $ 0 | $ 0 |

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- Definition Employee Stock Ownership Plan (ESOP), Debt Structure, Employer Loan, Amount + References No definition available. + Details
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- Definition Employee Stock Ownership Plan (ESOP), Shares Distributed to Participants + References No definition available. + Details
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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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- Definition The amount of plan compensation cost recognized during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480489/718-40-50-1 + Details
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- Definition Sum of the allocated, committed-to-be-released and suspense shares of the entity held by the plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480489/718-40-50-1 + Details
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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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- Definition Number of shares purchased for issuance under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (l) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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