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Inventories (Tables)
6 Months Ended
Jun. 30, 2021
Inventory Disclosure [Abstract]  
Schedule of Inventories
Inventories as of June 30, 2021 and December 31, 2020 consisted of the following:
June 30, 2021December 31, 2020
 (Dollars in millions)
Materials and supplies$101.5 $102.6 
Raw coal57.6 70.5 
Saleable coal73.4 88.5 
Total$232.5 $261.6