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Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Dec. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Accumulated Other Comprehensive Income (Loss), Net of Tax $ (30.7) $ (33.4) $ (30.7) $ (33.3)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax 0.0 (0.1)    
Pension Plan [Member]        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Accumulated Other Comprehensive Income (Loss), Net of Tax (41.9) (46.5) (42.0) (46.5)
Pension Plan [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax 0.0 0.0    
Other Postretirement Benefits Plan [Member]        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Accumulated Other Comprehensive Income (Loss), Net of Tax 11.2 13.2 $ 11.3 $ 13.3
Other Postretirement Benefits Plan [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax $ (0.1) $ (0.1)