Derivative Instruments and Hedging Activities (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
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)	$ 41	$ 6
Revenues [Member]
Commodity Derivative Activity Recorded in Statement of Consolidated Operations
Gain (loss) on derivatives recognized in operations (ineffective portion and basis swaps)	$ (1)	$ (3)