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Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Pension Benefits        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Service cost $ 0.6 $ 0.7 $ 1.9 $ 2.0
Interest cost 3.8 3.4 10.6 10.1
Expected return on plan assets (3.3) (3.9) (11.2) (11.8)
Amortization of prior service benefit (cost) 0.1 0.1 0.2 0.2
Amortization of net loss 0.9 1.4 3.8 4.4
Net periodic benefit cost 2.1 1.7 5.3 4.9
Other Postretirement Benefits        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Service cost 0.0 0.0 0.1 0.1
Interest cost 1.2 1.0 3.1 2.9
Amortization of prior service benefit (cost) 0.0 0.0 0.0 (0.1)
Amortization of net loss 0.4 0.2 0.7 0.5
Net periodic benefit cost $ 1.6 $ 1.2 $ 3.9 $ 3.4