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Intangible Assets (Tables)
12 Months Ended
Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]  
Schedule of Finite-Lived Intangible Assets The gross and net balances are set forth in the following table:
 Gross Carrying
Amount
Accumulated
Amortization
Net
Balance
Balance at December 31, 2021   
Coal supply agreement$84,200 $(52,426)$31,774 
Balance at December 31, 2020   
Coal supply agreement$84,200 $(48,870)$35,330