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Equity Method Investments	3 Months Ended
Equity Method Investments	Mar. 31, 2020
Equity Method Investments [Abstract]
Equity Method Investment	(15)EQUITY METHOD INVESTMENTS We own a 50% interest in Sunrise Energy, LLC, which owns gas reserves and gathering equipment with plans to develop and operate such reserves. Sunrise Energy also plans to develop and explore for oil, gas, and coal-bed methane gas reserves on or near our underground coal reserves. The carrying value of the investment included in our condensed consolidated balance sheets as of March 31, 2020, and December 31, 2019, was $3.3 million and $3.1 million, respectively.