Exploration, Geologic, and Geophysical Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Dry Hole Costs	$ 41,187	$ 0	$ 41,187	$ 0
Geological and geophysical	463	0	1,790	0
Exploratory operating costs	258	241	918	688
Costs Incurred, Exploration Costs	$ 41,908	$ 241	$ 43,895	$ 688