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LONG-LIVED ASSET IMPAIRMENTS (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2020
USD ($)
Asset impairment charges  
Asset impairments $ 24,977
Illinois Basin Coal Operations  
Asset impairment charges  
Asset impairments 23,500
Coal Royalties  
Asset impairment charges  
Asset impairments $ 1,500