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Employee Stock Ownership and 401(k) Plan: Narrative (Details) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 1998 USD ($) shares | Sep. 30, 2025 USD ($) component shares | Sep. 30, 2024 USD ($) shares | Sep. 30, 2023 USD ($) shares
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |  |
ESOP shares (in shares) | shares |  | 268,097 | 272,161 | 317,094
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 | $ |  | $ 1,086,000 | $ 1,084,000 | $ 1,039,000
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 |  | 789,903 |  |
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 Share-based Compensation Arrangement by Share-based Payment Award, Employee Minimum Age Requirement + 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://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480489/718-40-50-1 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480459/718-40-55-20 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480459/718-40-55-9 + 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://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480459/718-40-55-20 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480459/718-40-55-9 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 718 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480489/718-40-50-1 + Details
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