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Equity Method Investments	6 Months Ended
Equity Method Investments	Jun. 30, 2017
Equity Method Investments [Abstract]
Equity Method Investment	(3)Equity Method Investments We own a 30.6% interest in Savoy Energy, L.P., a private company engaged in the oil and gas business primarily in the State of Michigan. We also 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.