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Pension and Other Postretirement Benefits (Schedule of Benefit Obligations in Excess of Fair Value) (Details) - USD ($)
$ in Millions
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Pension Plan      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined Benefit Plan, Accumulated Benefit Obligation $ 1,390.9 $ 1,416.8  
Defined Benefit Plan, Benefit Obligation 1,401.8 1,427.4 $ 1,852.4
Defined Benefit Plan, Funded (Unfunded) Status of Plan 25.0 (4.6)  
Other Postretirement Benefits      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined Benefit Plan, Benefit Obligation 468.8 449.0 $ 556.2
Defined Benefit Plan, Funded (Unfunded) Status of Plan (232.3) (224.1)  
Underfunded Plan [Member] | Pension Plan      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined Benefit Plan, Accumulated Benefit Obligation 19.1 22.9  
Defined Benefit Plan, Benefit Obligation 19.1 22.9  
Defined Benefit Plan, Plan Assets, Amount 0.0 0.0  
Defined Benefit Plan, Funded (Unfunded) Status of Plan (19.1) (22.9)  
Underfunded Plan [Member] | Pension Plan      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined Benefit Plan, Accumulated Benefit Obligation 1,371.8 1,393.8  
Defined Benefit Plan, Benefit Obligation 1,382.7 1,404.5  
Defined Benefit Plan, Plan Assets, Amount 1,426.8 1,422.8  
Defined Benefit Plan, Funded (Unfunded) Status of Plan $ 44.1 $ 18.3