Suspended Well Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Dec. 31, 2011
Exploratory Wells Drilled [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period of One Year or Less	$ 59,243	$ 59,243
Capitalized Exploratory Well Costs	59,243	59,243	18,600
Results of Operations, Dry Hole Costs	3,600	(18,540)
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves		74,359
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves		(15,176)
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	$ 0	$ 0
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects	0	0
Exploratory Wells Drilled, Net Nonproductive		2