Capitalized Exploratory Well Costs Rollforward (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 well	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized exploratory well costs at beginning of period	$ 79,791	$ 70,437	$ 21,438
Additions pending determination of proved reserves	421,599	406,226	178,005
Reclassifications due to determination of proved reserves	(442,909)	(396,872)	(129,006)
Exploratory well costs charged to expense	(881)	0	0
Capitalized exploratory well costs at end of period	57,600	79,791	70,437
Exploratory wells in progress	14,794	77,693	70,437
Capitalized exploratory well costs for a period of one year or less	42,481	0	0
Capitalized exploratory well costs for a period greater than one year	1,206	2,098	0
Total capitalized exploratory well costs	$ 58,481	$ 79,791	$ 70,437
Wells in Process of drilling or waiting on results from completion and testing	48