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Pension and Postretirement Benefit Plans (Net Pension And Postretirement Cost) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2024
Sep. 30, 2023
Pension benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 2.0 $ 2.4 $ 6.2 $ 7.2
Interest cost 7.0 7.5 20.9 22.0
Expected return on plan assets (7.7) (7.5) (23.1) (22.1)
Amortization of net actuarial losses 2.3 2.2 6.7 6.4
Amortization of prior service cost 0.4 0.3 1.1 1.0
Net periodic cost 4.0 4.9 11.8 14.5
Postretirement benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0.0 0.0 0.1 0.0
Interest cost 0.4 0.4 1.2 1.0
Amortization of prior service cost 0.0 0.0 0.1 0.1
Net periodic cost $ 0.4 $ 0.4 $ 1.4 $ 1.1