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Employee Benefit Plans (Tables) | 9 Months Ended
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Sep. 30, 2025
Defined Benefit Plan Disclosure [Line Items] |
Components of Net Periodic Benefit Cost | The components of net periodic expense were as follows:
| Defined Benefit Pension Plan |  | Supplemental Non-qualified Defined Benefit Plans |  | Non-pension Defined Benefit Postretirement Healthcare Plan |
Three Months Ended September 30, | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |
| (in millions) |
Service cost | $ | 0.4 |  | $ | 0.6 |  | $ | 1.2 |  | $ | 1.3 |  | $ | 0.4 |  | $ | 0.4 |
Interest cost |  | 4.0 |  |  | 4.1 |  |  | 0.3 |  |  | 0.4 |  |  | 0.6 |  |  | 0.6 |
Expected return on plan assets |  | (4.2 | ) |  | (4.5 | ) |  | — |  |  | — |  |  | (0.1 | ) |  | (0.1 | )
Net amortization of prior service costs |  | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | 0.1 |
Recognized net actuarial loss |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |  |  | — |  |  | — |
Net periodic expense | $ | 0.7 |  | $ | 0.7 |  | $ | 1.5 |  | $ | 1.7 |  | $ | 1.0 |  | $ | 1.0 |
| Defined Benefit Pension Plan |  | Supplemental Non-qualified Defined Benefit Plans |  | Non-pension Defined Benefit Postretirement Healthcare Plan |
Nine Months Ended September 30, | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |
| (in millions) |
Service cost | $ | 1.3 |  | $ | 1.7 |  | $ | 2.8 |  | $ | 2.9 |  | $ | 1.1 |  | $ | 1.2 |
Interest cost |  | 12.0 |  |  | 12.3 |  |  | 1.1 |  |  | 1.1 |  |  | 1.8 |  |  | 1.8 |
Expected return on plan assets |  | (12.7 | ) |  | (13.4 | ) |  | — |  |  | — |  |  | (0.2 | ) |  | (0.2 | )
Net amortization of prior service costs |  | (0.1 | ) |  | (0.1 | ) |  | — |  |  | — |  |  | 0.2 |  |  | 0.1 |
Recognized net actuarial loss |  | 1.6 |  |  | 1.5 |  |  | — |  |  | — |  |  | — |  |  | — |
Net periodic expense | $ | 2.1 |  | $ | 2.0 |  | $ | 3.9 |  | $ | 4.0 |  | $ | 2.9 |  | $ | 2.9 |
Schedule of Employer Contribution to Employee Benefit Plans | Contributions made in the first nine months of 2025 and additional contributions anticipated for the remainder of 2025 are as follows:
| Contributions Made |  | Additional Contributions |
| Nine Months Ended September 30, 2025 |  | Anticipated for 2025 |
| (in millions) |
Defined Benefit Pension Plan | $ | 1.8 |  | $ | — |
Non-pension Defined Benefit Postretirement Healthcare Plan |  | 3.5 |  |  | 1.2 |
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans |  | 2.1 |  |  | 0.7 |

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