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Commitments and Contingencies (Details)
$ in Millions
Jun. 30, 2023
USD ($)
Dec. 31, 2022
USD ($)
Oct. 09, 2015
buyer
Dec. 31, 2007
USD ($)
Patriot        
Long-term Purchase Commitment [Line Items]        
Number of buyers | buyer     2  
Black Lung Occupational Disease Liability | Patriot | Spinoff        
Long-term Purchase Commitment [Line Items]        
Initially determined potential exposure from patriot bankruptcy       $ 150.0
Black Lung Occupational Disease Liability | Patriot | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations        
Long-term Purchase Commitment [Line Items]        
Initially determined potential exposure from patriot bankruptcy $ 80.0 $ 82.3    
Capital Addition Purchase Commitments        
Long-term Purchase Commitment [Line Items]        
Unrecorded unconditional purchase obligation (within next five years) 100.8      
Unrecorded unconditional purchase obligation (within next 12 months) $ 94.1