Suspended Well Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Beginning balance	$ 49,446	$ 19,846	$ 11,952
Additions to capitalized exploratory well costs pending the determination of proved reserves	11,197	49,446	19,846
Divestitures	(109)	0	0
Reclassification to wells, facilities, and equipment based on the determination of proved reserves	(49,337)	(19,846)	(11,952)
Capitalized exploratory well costs charged to expense	0	0	0
Ending balance	11,197	$ 49,446	$ 19,846
Exploratory well costs capitalized for more than one year	$ 0