Asset Acquisitions, Dispositions and Other Transactions (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2010 Libya activity boe barrel	Sep. 30, 2011 Libya activity
Asset acquisitions, dispositions and other transactions
Capitalized and suspended exploration costs written off	$ 35
Net book value of Libyan producing properties			800
Proved reserves, net (in barrels)		57,000,000
Net proved reserves as a percentage of total proved reserves (as a percent)		2.00%
Sales and production volumes (BOE per day)		13,000
Sales and production volumes as a percentage of worldwide sales and production volumes (as a percent)		2.00%
After-tax income from Libyan operations, excluding exploration costs		25
After-tax cashflows from Libyan operations, excluding exploration costs		$ 31