Exploratory Well Costs (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capitalized Exploratory Well Costs [Abstract]
Balance at January 1		$ 17,253	$ 9,211	$ 49,116
Additions Pending the Determination of Proved Reserves		24,640	32,080	52,099
Reclassifications to Proved Properties		(26,659)	(15,946)	(54,505)
Costs Charged to Expense (1)	[1]	(6,279)	(8,092)	(35,859)
Foreign Currency Translations		0	0	(1,640)
Balance at December 31		$ 8,955	$ 17,253	$ 9,211

[1] Includes capitalized exploratory well costs charged to either dry hole costs or impairments.