Suspended Well Costs (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period of One Year or Less	$ 15,618	$ 35,862	$ 34,384
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	2,982	0	0
Capitalized Exploratory Well Costs	18,600	35,862	34,384
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized Exploratory Well Costs Beginning Balance	35,862	34,384	9,437
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves	15,618	35,862	34,384
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves	(32,880)	(34,384)	(7,569)
Capitalized Exploratory Well Cost, Charged to Expense	0	0	(1,868)
Capitalized Exploratory Well Costs Ending Balance	$ 18,600	$ 35,862	$ 34,384
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects	2	0	0