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Summary of Significant Accounting Policies (Details)
$ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
Employee
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Property, Plant and Equipment      
Interest costs capitalized | $ $ 0.2 $ 2.3 $ 3.2
Labor Concentrations      
Number of employees 841    
Percentage of domestic employees 3.00%    
Brazil      
Labor Concentrations      
Number of employees 292    
Cokemaking Operations      
Labor Concentrations      
Number of employees 0.41    
Coke and energy plant, machinery and equipment | Minimum      
Property, Plant and Equipment      
Useful life 25 years    
Coke and energy plant, machinery and equipment | Maximum      
Property, Plant and Equipment      
Useful life 30 years    
Logistics plant, machinery and equipment | Minimum      
Property, Plant and Equipment      
Useful life 15 years    
Logistics plant, machinery and equipment | Maximum      
Property, Plant and Equipment      
Useful life 35 years