Supplemental Oil and Gas Disclosures Costs Incurred (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Company
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Development costs—other	$ 0	$ 0	$ 0
Total	0	0	0
Company's Share of Laramie Energy
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Acquisition costs	0	0	65,324
Development costs—other	50,867	49,273	12,805
Total	$ 50,867	$ 49,273	$ 78,129