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Employee Benefits - Summary of Components of Net Periodic Postretirement Benefit Cost (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items] |  |  |
Net periodic postretirement benefit cost | $ 5.6 | $ 4.1 | $ 4.7
Salaried VEBA |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 0.1 | 0.1 |
Interest cost | 1.9 | 1.5 |
Pension Plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 5.8 | 4.1 | 0.3
Interest cost | 0.6 | 0.5 | 0.3
Expected return on plan assets | $ (0.9) | $ (0.4) | $ (0.3)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Amortization of net actuarial loss |  | $ 0.1 | $ 0.1
Net periodic postretirement benefit cost | $ 5.5 | 4.3 | 0.4
Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 1.6 | 1.1 |
Interest cost | 2.2 | 1.7 |
Net periodic postretirement benefit cost | 3.8 | 2.8 |
Postretirement Health Coverage | Salaried VEBA |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 0.1 | 0.1 | 0.1
Interest cost | 1.9 | 1.5 | 2.5
Expected return on plan assets | (3.1) | (3.1) | (2.8)
Amortization of prior service cost | $ 4.9 | $ 3.5 | $ 4.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration] | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Amortization of net actuarial loss |  | $ 0.3 | $ 0.3
Net periodic postretirement benefit cost | $ 3.8 | $ 2.3 | $ 4.8

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