Exploratory Well Costs (Capitalized Exploratory Costs And the Number Of Projects For Which Exploratory Costs Have Been Capitalized) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Exploratory Well Costs [Abstract]
One year or less	$ 107,596	$ 70,635	$ 21,634
More than one year		25,558	105,940
Capitalized exploratory well costs, total suspended	$ 107,596	$ 96,193	$ 127,574
Number of projects with exploratory well costs that have been suspended for a period greater than one year		3	8