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Pension and Postretirement Benefit Costs - Schedule of Net Periodic Benefit (Benefit) Cost (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]    
Net periodic pension credit $ (12.2) $ (8.7)
Defined benefit pension plans    
Defined Benefit Plan Disclosure [Line Items]    
Interest cost on projected benefit obligation 5.3 5.1
Expected return on plan assets (5.9) (5.7)
Net periodic pension credit (0.6) (0.6)
Postretirement benefit plans    
Defined Benefit Plan Disclosure [Line Items]    
Service cost for benefits earned 0.2 0.2
Interest cost on projected benefit obligation 1.7 2.9
Expected return on plan assets (0.2) (0.2)
Amortization of prior service credit (13.4) (11.0)
Net periodic pension credit $ (11.7) $ (8.1)