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Savings, Pension and Other Postretirement Employee Benefit Plans - Changes in Benefit Obligation, Plan Assets and Funded Status for Company-Sponsored Benefit Plans (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]      
Liability for pension and other postretirement employee benefits $ (55.7) $ (58.2)  
Pension Benefit Plans      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of year 234.7 310.1  
Service cost 3.5 2.2 $ 1.8
Interest cost 12.5 8.9 8.4
Actuarial losses (gains) 0.1 (65.5)  
Defined Benefit Plan, Benefit Obligation, Benefits Paid (22.4) (21.0)  
Benefit obligation at end of year 228.3 234.7 310.1
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets at beginning of year 231.7 317.5  
Actual return on plan assets 21.2 (65.3)  
Employer contribution 0.5 0.5  
Defined Benefit Plan, Plan Assets, Benefits Paid 22.4 21.0  
Fair value of plan assets at end of year 231.1 231.7 317.5
Funded status at end of year 2.8 (3.0)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan (2.8) 3.0  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]      
Assets for Plan Benefits, Defined Benefit Plan 11.1 8.4  
Current liability for pension and other postretirement employee benefits (0.5) (0.4)  
Liability for pension and other postretirement employee benefits (7.9) (11.0)  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position 2.8 (3.0)  
Net actuarial loss (gain) 56.4 62.5  
Other Postretirement Employee Benefit Plans      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of year 52.2 71.9  
Service cost 0.2 0.3 0.4
Interest cost 2.8 2.1 2.0
Actuarial losses (gains) 2.2 (17.3)  
Defined Benefit Plan, Benefit Obligation, Benefits Paid (4.9) (4.8)  
Benefit obligation at end of year 52.5 52.2 71.9
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets at beginning of year 0.0 0.0  
Actual return on plan assets 0.0 0.0  
Employer contribution 4.9 4.8  
Defined Benefit Plan, Plan Assets, Benefits Paid 4.9 4.8  
Fair value of plan assets at end of year 0.0 0.0 $ 0.0
Funded status at end of year (52.5) (52.1)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan 52.5 52.1  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]      
Assets for Plan Benefits, Defined Benefit Plan 0.0 0.0  
Current liability for pension and other postretirement employee benefits (4.7) (4.9)  
Liability for pension and other postretirement employee benefits (47.8) (47.2)  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position (52.5) (52.1)  
Net actuarial loss (gain) $ (8.9) $ (11.5)