Exploratory Well Costs (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Exploratory Well Costs [Abstract]
Balance at December 31, 2012	$ 49,116
Additions Pending the Determination of Proved Reserves	64,343
Reclassifications to Proved Properties	(49,742)
Costs Charged to Expense (1)	(31,006)	[1]
Foreign Currency Translations	(1,355)
Balance at September 30, 2013	$ 31,356

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