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Employee Benefit Plans (Principal Components of Employee Benefit Costs) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Employee Benefit Plan Disclosure [Line Items]      
Pension and Other Postretirement Benefits Cost (Reversal of Cost) $ 73.6 $ 34.8 $ 108.7
Savings Plan      
Employee Benefit Plan Disclosure [Line Items]      
Savings plan 34.5 37.3 73.7
Unfunded Supplemental Benefit Plans      
Employee Benefit Plan Disclosure [Line Items]      
Employee benefit plan expenses 12.3 12.2 10.6
Other Plans, Net      
Employee Benefit Plan Disclosure [Line Items]      
Other plans, net [1] $ 26.8 $ (14.7) $ 24.4
[1] For the year ended December 31, 2022, participant investments included in the deferred compensation plan realized losses in excess of expenses recorded by the Company.