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Pension and Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Credit) (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Pension    
Defined Benefit Plan Disclosure [Line Items]    
Service cost $ 7.7 $ 11.5
Interest cost 12.7 10.2
Expected return on assets (17.8) (19.4)
Prior service cost (credit) 1.4 1.2
Actuarial loss (gain) 0.1 0.9
Net periodic benefit cost (credit) 4.1 4.4
Postretirement Benefits    
Defined Benefit Plan Disclosure [Line Items]    
Service cost 0.0 0.0
Interest cost 0.1 0.1
Expected return on assets 0.0 0.0
Prior service cost (credit) (0.1) (0.2)
Actuarial loss (gain) (0.1) (0.1)
Net periodic benefit cost (credit) $ (0.1) $ (0.2)