Asset Acquisitions, Dispositions and Other Transactions (Details) (Shah Field high sulfur content gas development project, USD $)	3 Months Ended
	Mar. 31, 2011	May 31, 2011
Shah Field high sulfur content gas development project
Asset acquisitions, dispositions and other transactions
Percentage of interest acquired in oil and gas properties and projects (as a percent)	40.00%
Term of joint venture agreement (in years)	30
Total project amount	$ 10,000,000,000
Joint venture, entity's portion	4,000,000,000
Share of previously incurred development expenditures paid		$ 500,000,000