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Pension and Other Postemployment Benefits | 9 Months Ended
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Sep. 30, 2025
Pension and Other Postemployment Benefits [Abstract] |
Pension and Other Postemployment Benefits | Pension and Other Postemployment Benefits Pension and other postemployment benefits net periodic benefit expense:
| Defined Benefit Pension Plans |  | Postemployment Arrangements
| Nine Months Ended September 30, |  | Nine Months Ended September 30,
| 2025 |  | 2024 |  | 2025 |  | 2024
Service cost | $ | 3.7 |  |  | $ | 2.1 |  |  | $ | 1.6 |  |  | $ | 2.3 |
Interest cost | 6.1 |  |  | 4.9 |  |  | 4.1 |  |  | 4.4 |
Expected return on plan assets | (0.6) |  |  | (0.6) |  |  | — |  |  | — |
Amortization of prior service cost | 2.3 |  |  | 0.3 |  |  | 2.8 |  |  | 3.3 |
Amortization of actuarial losses | 0.7 |  |  | 0.6 |  |  | — |  |  | 0.2 |
Total net periodic benefit expense | $ | 12.2 |  |  | $ | 7.3 |  |  | $ | 8.5 |  |  | $ | 10.2 |
In each of the nine months ended September 30, 2025 and 2024, we contributed $0.5 million and $1.2 million, respectively, to the defined benefit pension plans.

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