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Employee Benefit Plans and Other Postretirement Benefits - Summary of Changes in Pension Plans' Level 3 Assets (Details) - Pension Plans $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Level 3 fair value of pension plans' assets [Roll Forward] |
Plan assets at fair value at beginning of period | $ 1,073.8
Fair value of plan assets at plan year end | 1,300.7
Significant unobservable input (Level 3) | Private Equity Securities |
Level 3 fair value of pension plans' assets [Roll Forward] |
Plan assets at fair value at beginning of period | 2.6
Sales | (0.6)
Fair value of plan assets at plan year end | $ 2.0

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