Exploratory Well Costs (Capitalized Exploratory Well And Project Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Exploratory Well Costs [Abstract]
Beginning capitalized exploratory well costs	$ 96,193,000		$ 127,574,000		$ 124,014,000
Additions to exploratory well costs pending the determination of proved reserves	524,313,000		238,905,000		80,222,000
Reclassification due to determination of proved reserves	(480,716,000)		(160,879,000)		(58,792,000)
Disposition of assets sold	(28,938,000)		(17,601,000)
Exploratory well costs charged to exploration expense	(3,256,000)	[1]	(91,806,000)	[1]	(17,870,000)	[1]
Ending capitalized exploratory well costs	107,596,000		96,193,000		127,574,000
Exploratory well credit of discontinued operations			117,000
Exploratory well cost of discontinued operations					$ 9,900,000

[1] Includes an exploratory well credit included in discontinued operations of $117 thousand in 2010, and exploratory well costs included in discontinued operations of $9.9 million in 2009.