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Other Postretirement Benefit Plans - Schedule of Changes in Prior Service Cost Recognized in Accumulated Other Comprehensive Loss (Income) (Details) - Postretirement Plan - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Changes to prior service credit recognized in accumulated other comprehensive loss:    
Accumulated other comprehensive loss at beginning of year $ (63.6) $ (71.9)
Recognized prior service credit 8.2 8.3
Accumulated other comprehensive loss (income) at end of year $ (55.4) $ (63.6)