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Related party transactions	6 Months Ended
Related party transactions	Jun. 30, 2017
Related Party Transactions [Abstract]
Related party transactions	Note 11. Related party transactions The Company paid royalties on certain properties to a partnership in which a director of the Company is the general partner and owns a 3.5 percent partnership interest. These payments were reported in the Company’s consolidated statements of operations and totaled approximately $2 million and $1 million for the three months ended June 30, 2017 and 2016, respectively, and approximately $4 million and $2 million for the six months ended June 30, 2017 and 2016, respectively.