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Employee Benefits - Summary of Components of Net Periodic Postretirement Benefit Cost (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items] |  |
Total net periodic postretirement benefit cost (credit) | $ 0.3 | $ 2.0
Pension Plans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Service cost | 0.9 | 1.0
Interest cost | 0.4 | 0.3
Expected return on plan assets | (0.3) | (0.3)
Amortization of prior service cost (credit) | 0.2 |
Total net periodic postretirement benefit cost (credit) | 1.2 | 1.0
Other Postretirement Benefits Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Service cost | 0.3 | 0.3
Interest cost | 0.8 | 0.8
Amortization of net actuarial gain | (0.3) | (0.3)
Total net periodic postretirement benefit cost (credit) | 0.8 | 0.8
Postretirement Health Coverage | Salaried VEBA |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Interest cost | 0.5 | 0.7
Expected return on plan assets | (0.5) | (0.6)
Amortization of prior service cost (credit) | (0.5) | 1.2
Total net periodic postretirement benefit cost (credit) | $ (0.5) | $ 1.3

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