v3.25.2
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 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]        
Net periodic pension cost     $ 9.6 $ 5.1
Defined Benefit Pension Plan [Member]        
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]        
Interest cost $ 5.7 $ 4.1 11.4 8.2
Actuarial loss (gain) amortization 5.0 3.3 10.0 6.6
Less: Expected return on plan assets (5.5) (4.4) (11.0) (8.8)
Net periodic pension cost 5.2 3.0 10.4 6.0
Other Postretirement Benefits Plan [Member]        
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]        
Interest cost 0.1 0.1 0.2 0.2
Actuarial loss (gain) amortization (0.5) (0.6) (1.0) (1.1)
Net periodic pension cost $ (0.4) $ (0.5) $ (0.8) $ (0.9)