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Net Periodic Benefit Cost for Period Reconciliation of Changes in Plan Assets Projected Benefit Obligations and Amounts Recognized in Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) - Frozen Defined Benefit Pension Plans - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021
Net Periodic Pension Cost in Income Statement |  |  |  |
Net Periodic Pension Cost in Income Statement, Interest cost | $ 2,133 | $ 2,312 | $ 1,560 |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest Income (Expense), Operating and Nonoperating | Interest Income (Expense), Operating and Nonoperating | Interest Income (Expense), Operating and Nonoperating |
Net Periodic Pension Cost in Income Statement, Actual return on plan assets | $ (6,672) | $ (1,196) | $ 13,151 |
Net Periodic Pension Cost in Income Statement, Difference between actual and expected return on plan assets | 4,558 | (635) | (15,200) |
Net Periodic Pension Cost in Income Statement, Amortization of unrecognized net actuarial loss | 1,277 | 1,526 | 896 |
Net Periodic Pension Cost in Income Statement, Annual cost/change | 1,296 | 2,007 | 407 |
Cash |  |  |  |
Cash, Employer contributions/ Annual cost/change |  | (64) |  |
Fair Value of Pension Plan Assets |  |  |  |
Fair Value of Pension Plan Assets, Beginning Balance | 44,206 | 47,454 | 65,337 |
Fair Value of Pension Plan Assets, Actual return on plan assets | 6,672 | 1,196 | (13,151) |
Fair Value of Pension Plan Assets, Employer contributions |  | 64 |  |
Fair Value of Pension Plan Assets, Benefit payments | (3,649) | (3,936) | (4,225) |
Fair Value of Pension Plan Assets, Investment and other expenses | (239) | (572) | (507) |
Fair Value of Pension Plan Assets, Annual cost/change | 2,784 | (3,248) | (17,883) |
Fair Value of Pension Plan Assets, Ending Balance | 46,990 | 44,206 | 47,454 |
Projected Benefit Obligation |  |  |  |
Projected Benefit Obligation, Beginning balance | (41,485) | (44,253) | (61,294) |
Projected Benefit Obligation, Interest cost | (2,133) | (2,312) | (1,560) |
Projected Benefit Obligation, Benefit payments | 3,649 | 3,936 | 4,225 |
Projected Benefit Obligation, Investment and other expenses | 239 | 572 | 507 |
Projected Benefit Obligation, Actuarial (loss) gain | (4,544) | 572 | 13,869 |
Projected Benefit Obligation, Annual cost/change | (2,789) | 2,768 | 17,041 |
Projected Benefit Obligation, Ending balance | (44,274) | (41,485) | (44,253) |
Funded status at the end of the year | 2,716 | 2,721 | 3,201 | $ 4,043
Other Comprehensive (Income) / Loss |  |  |  |
Other Comprehensive (Income) / Loss, Difference between actual and expected return on plan assets | (4,558) | 635 | 15,200 |
Other Comprehensive (Income) / Loss, Actuarial loss (gain) | 4,544 | (572) | (13,869) |
Other Comprehensive (Income) / Loss, Amortization of unrecognized net actuarial loss | (1,277) | (1,526) | (896) |
Other Comprehensive (Income) / Loss, Annual cost/change | (1,291) | (1,463) | 435 |
Gross Pension Related Accumulated Other Comprehensive Income |  |  |  |
Gross Pension Related Accumulated Other Comprehensive Income, Beginning Balance | 10,465 | 11,928 | 11,493 |
Other Comprehensive (Income) / Loss, Annual cost/change | (1,291) | (1,463) | 435 |
Gross Pension Related Accumulated Other Comprehensive Income, Ending Balance | $ 9,174 | $ 10,465 | $ 11,928 |

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