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Employee Benefit Plans - Narrative (Details) | 12 Months Ended
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Sep. 30, 2024 USD ($) installment $ / shares shares | Sep. 30, 2023 USD ($) | Sep. 30, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |
Employee contribution, percentage of annual salary | 100.00% |  |
Employee contribution, maximum allowable contribution | $ | $ 69,000 |  |
Service period for participation eligibility | 30 days |  |
Service period for eligibility of profit sharing or matching contributions | 1 year |  |
Employer matching contribution percent | 100.00% |  |
Percent of employees' gross pay | 4.00% |  |
Profit sharing contribution, vesting schedule (in years) | 6 years |  |
Company contributions to plan | $ | $ 8,185,000 | $ 8,648,000 | $ 10,559,000
Employee Stock |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Purchase price of common stock, percent | 95.00% |  |
Shares available for issuance (in shares) | shares | 500,000 |  |
Shares purchased (in shares) | shares | 35,782 |  |
Shares purchased, amount | $ | $ 956,550 |  |
Remaining shares available (in shares) | shares | 457,191 |  |
SERP |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Number of annual installments | installment | 10 |  |
Amount authorized | $ | $ 11,700,000 |  |
Units credited in period (in shares) | shares | 12,710 |  |
Units outstanding (in shares) | shares | 388,968 |  |
Weighted average grant date fair value (in dollars per share) | $ / shares | $ 31.56 |  |
Employee benefits related expenses | $ | $ 1,013,000 |  |

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