Suspended Well Costs Suspended Well Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized Exploratory Well Costs Beginning Balance	$ 11,952	$ 43,589	$ 34,527
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves	19,846	11,952	43,589
Capitalized Exploratory Well Cost, Divestitures	0	(809)	0
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves	(11,952)	(18,485)	(33,340)
Capitalized Exploratory Well Cost Charged to Expense	0	(24,295)	(1,187)
Capitalized Exploratory Well Costs Ending Balance	19,846	$ 11,952	$ 43,589
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	$ 0