v3.25.2
Defined Benefit and Postretirement Benefits (Components Of Net Periodic Cost) (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Pension        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 0.9 $ 0.9 $ 1.7 $ 1.8
Interest cost 8.6 8.7 17.2 17.3
Expected return on plan assets (11.1) (12.5) (22.1) (25.0)
Amortization of prior service cost 0.2 0.2 0.4 0.4
Amortization of net loss (gain) 3.5 3.7 7.0 7.5
Net periodic loss (benefit) 2.1 1.0 4.2 2.0
Pension | Discontinued Operations        
Defined Benefit Plan Disclosure [Line Items]        
Net periodic loss (benefit)   0.1    
Postretirement        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0.0 0.0 0.0 0.0
Interest cost 0.1 0.0 0.1 0.1
Expected return on plan assets 0.0 0.0 0.0 0.0
Amortization of prior service cost 0.0 0.0 0.0 0.0
Amortization of net loss (gain) (0.1) (0.1) (0.2) (0.2)
Net periodic loss (benefit) $ 0.0 $ (0.1) $ (0.1) (0.1)
Postretirement | Discontinued Operations        
Defined Benefit Plan Disclosure [Line Items]        
Net periodic loss (benefit)       $ 0.3