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Pension Benefits - Narrative (Details) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2024 | Jun. 30, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Sep. 30, 2024
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined contribution plan, cost |  |  | $ 24,300,000 | $ 27,500,000 | $ 30,600,000 |
Pension Plans |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Settlement of asset retirement obligations |  |  | 70,200,000 |  |  |
Settlement of asset retirement obligations |  |  | 55,500,000 |  |  |
Assets for plan benefits | $ 0 |  | 0 | 16,300,000 |  | $ 17,800,000
Settlement adjustment |  | $ 2,700,000 |  |  |  |
Reversion of assets | 4,700,000 |  |  |  |  |
Corporate use | 13,100,000 |  | 13,100,000 |  |  |
Reversion of assets, expenses | 7,300,000 |  |  |  |  |
Excise tax | 2,600,000 |  | 2,600,000 |  |  |
Unfunded liability | 0 |  | 0 | (16,300,000) |  |
Pension expense |  |  | (2,600,000) | 71,100,000 | 3,800,000 |
Unrecognized pension gain (loss) arising during the year |  |  | 0 | 0 | 12,000,000.0 |
Supplemental Employee Retirement Plan |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Unfunded liability | $ 20,100,000 |  | 20,100,000 | 21,800,000 |  |
Pension expense |  |  | 1,000,000.0 | 1,000,000.0 | 800,000 |
Unrecognized pension gain (loss) arising during the year |  |  | $ 800,000 | $ (700,000) | $ 4,800,000 |

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