Derivative Instruments and Hedging Activities (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Oil and Gas Production Revenues [Member]
Commodity Derivative Activity Recorded in Statement of Consolidated Operations
Gain (loss) reclassified from accumulated other comprehensive income (loss) into operations (effective portion)	$ (13)	$ 165	$ 181
Revenues [Member]
Commodity Derivative Activity Recorded in Statement of Consolidated Operations
Gain (loss) on derivatives recognized in operations (ineffective portion and basis swaps)	$ 2	$ (2)	$ (4)