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Inventories (Details) - USD ($)
$ in Millions
Dec. 31, 2022
Dec. 31, 2021
Inventory Disclosure [Abstract]    
Inventory adjustments $ 2.6  
Coal 109.4 $ 63.5
Coke 14.3 16.6
Materials, supplies and other 51.5 46.9
Total inventories $ 175.2 $ 127.0