v3.25.1
Employee Benefit Plans - Components of Net Periodic Cost for Defined Benefit Pension Plan and for Postretirement Benefit Plan (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]    
Net periodic pension cost $ 4.8 $ 2.6
Defined Benefit Pension Plan [Member]    
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]    
Interest cost 5.7 4.1
Actuarial loss (gain) amortization 5.0 3.3
Less: Expected return on plan assets (5.5) (4.4)
Net periodic pension cost 5.2 3.0
Other Postretirement Benefits Plan [Member]    
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]    
Interest cost 0.1 0.1
Actuarial loss (gain) amortization (0.5) (0.5)
Net periodic pension cost $ (0.4) $ (0.4)