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Commitments and Contingencies (Details)
$ in Millions
Sep. 30, 2022
USD ($)
Jul. 29, 2022
USD ($)
Dec. 31, 2021
USD ($)
Oct. 09, 2015
buyer
Dec. 31, 2007
USD ($)
Long-term Purchase Commitment [Line Items]          
Securities class action settlement   $ 4.6      
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 $ 85.7   $ 87.2   $ 150.0
Capital Addition Purchase Commitments          
Long-term Purchase Commitment [Line Items]          
Unrecorded unconditional purchase obligation (within next five years) 77.8        
Unrecorded unconditional purchase obligation (within next 12 months) $ 71.3