Financial Instruments, Derivatives, Guarantees and Concentration of Credit Risk (Details 4) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pre-tax gains and losses for our energy commodity derivatives not designated as hedging instruments
Net gain (loss)	$ 2	$ (22)	$ 4	$ 4
Revenues
Pre-tax gains and losses for our energy commodity derivatives not designated as hedging instruments
Net gain (loss)	2	(15)	4	11
Costs and operating expenses
Pre-tax gains and losses for our energy commodity derivatives not designated as hedging instruments
Net gain (loss)		$ 7		$ 7