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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, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]      
Liability for pension and other postretirement employee benefits $ (52.5) $ (54.5)  
Pension Benefit Plans      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of year 228.3 234.7  
Service cost 2.5 3.5 $ 2.2
Interest cost 11.9 12.5 8.9
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 0.0 0.0  
Actuarial losses (gains) (4.2) 0.1  
Defined Benefit Plan, Benefit Obligation, Benefits Paid (21.3) (22.4)  
Benefit obligation at end of year 217.2 228.3 234.7
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets at beginning of year 231.1 231.7  
Actual return on plan assets 3.5 21.2  
Employer contribution 1.1 0.5  
Defined Benefit Plan, Plan Assets, Benefits Paid 21.3 22.4  
Fair value of plan assets at end of year 214.4 231.1 231.7
Funded status at end of year (2.8) 2.8  
Defined Benefit Plan, Funded (Unfunded) Status of Plan 2.8 (2.8)  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]      
Assets for Plan Benefits, Defined Benefit Plan 8.7 11.1  
Current liability for pension and other postretirement employee benefits (0.5) (0.5)  
Liability for pension and other postretirement employee benefits (11.0) (7.9)  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position (2.8) 2.8  
Net actuarial loss (gain) 64.2 56.4  
Other Postretirement Employee Benefit Plans      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of year 51.3 50.9  
Service cost 0.2 0.2 0.3
Interest cost 2.5 2.8 2.1
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 0.2 0.0  
Actuarial losses (gains) (4.1) 2.2  
Defined Benefit Plan, Benefit Obligation, Benefits Paid (4.1) (4.9)  
Benefit obligation at end of year 45.9 51.3 50.9
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 4.1 4.9  
Defined Benefit Plan, Plan Assets, Benefits Paid 4.1 4.9  
Fair value of plan assets at end of year 0.0 0.0 $ 0.0
Funded status at end of year (45.9) (51.2)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan 45.9 51.2  
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 (4.4) (4.6)  
Liability for pension and other postretirement employee benefits (41.5) (46.6)  
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position (45.9) (51.2)  
Net actuarial loss (gain) $ (11.6) $ (8.9)