Properties and Equipment (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net changes in capitalized exploratory well costs
Balance at the beginning of the period	$ 10,390	$ 5,328	$ 4,285
Additions to capitalized exploratory well costs pending the determination of proved reserves		10,390	5,328
Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(10,198)		(1,138)
Capitalized exploratory well costs charged to expense	(192)	(5,328)	(3,147)
Balance at the end of the period		$ 10,390	$ 5,328