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Income Taxes - Reconciliation of the Federal Statutory Tax Rate to the Total Tax Provision (Benefit) (Detail) | 12 Months Ended
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Sep. 30, 2024 | Sep. 30, 2023
Income Tax Disclosure [Abstract] |  |
Federal income taxes computed at the statutory rate | 21.00% | 21.00%
State income taxes, net of federal benefit | 1.20% | 1.40%
Unrecognized tax benefits | 5.80% | 0.00%
Other, net | 1.80% | (0.50%)
Effective income tax rate | 29.80% | 21.90%

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