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Employee Benefits - Benefit Obligations and Funded Status of Pension Plans, OPEB and Salaried VEBAs (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Salaried VEBA |  |  |
Change in benefit obligation: |  |  |
Obligation at beginning of year | $ 79.8 | $ 78.3 |
Service cost | 0.1 | 0.1 |
Interest cost | 1.9 | 1.5 |
Prior service cost |  | 14.0 |
Actuarial (gain) loss | (16.3) | (6.9) |
Benefits paid | (6.6) | (7.2) |
Obligation at end of year | 58.9 | 79.8 | $ 78.3
Change in plan assets: |  |  |
Fair market value of plan assets at beginning of year | 59.2 | 60.5 |
Actual return on assets | (10.2) | 5.9 |
Benefits paid | (6.6) | (7.2) |
Fair market value of plan assets at end of year | 42.4 | 59.2 | 60.5
Net funded status | (16.5) | (20.6) |
Cumulative gain (loss) recognized in Accumulated Other Comprehensive Income (Loss): |  |  |
Accumulated net actuarial gain (loss) | 1.7 | (1.2) |
Prior service cost | (29.7) | (34.6) |
Total | (28.0) | (35.8) |
Pension Plans |  |  |
Change in benefit obligation: |  |  |
Obligation at beginning of year | 20.3 | 10.0 |
Obligation assumed through acquisition of Warrick |  | 6.5 |
Foreign currency translation adjustment | (0.5) |  |
Service cost | 5.8 | 4.1 | 0.3
Interest cost | 0.6 | 0.5 | 0.3
Actuarial (gain) loss | (7.1) | (0.3) |
Plan participants contributions | 0.1 |  |
Benefits paid | (0.4) | (0.5) |
Obligation at end of year | 18.8 | 20.3 | 10.0
Change in plan assets: |  |  |
Fair market value of plan assets at beginning of year | 9.8 | 8.7 |
Foreign currency translation adjustment | (0.5) |  |
Actual return on assets | (2.6) | 1.1 |
Plan participants contributions | 0.1 |  |
Company contributions | 8.5 | 0.5 |
Benefits paid | (0.4) | (0.5) |
Fair market value of plan assets at end of year | 14.9 | 9.8 | $ 8.7
Net funded status | (3.9) | (10.5) |
Cumulative gain (loss) recognized in Accumulated Other Comprehensive Income (Loss): |  |  |
Accumulated net actuarial gain (loss) | 2.6 | (1.0) |
Total | 2.6 | (1.0) |
Other Postretirement Benefits Plan |  |  |
Change in benefit obligation: |  |  |
Obligation at beginning of year | 83.5 |  |
Obligation assumed through acquisition of Warrick |  | 78.1 |
Service cost | 1.6 | 1.1 |
Interest cost | 2.2 | 1.7 |
Actuarial (gain) loss | (20.4) | 2.6 |
Plan participants contributions | 0.1 |  |
Benefits paid | (0.6) |  |
Obligation at end of year | 66.4 | 83.5 |
Change in plan assets: |  |  |
Plan participants contributions | 0.1 |  |
Company contributions | 0.5 |  |
Benefits paid | (0.6) |  |
Net funded status | (66.4) | (83.5) |
Cumulative gain (loss) recognized in Accumulated Other Comprehensive Income (Loss): |  |  |
Accumulated net actuarial gain (loss) | 17.8 | (2.6) |
Total | $ 17.8 | $ (2.6) |

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