Risk Management and Trading Activities (Details 1) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	$ (50)	$ (104)	$ 2	$ 29
Corporate Risk Management [Member] | Foreign Exchange Contracts [Member] | Not designated as hedges [Member]
Net pre-tax gains (losses) on derivative contracts not designated as hedges
Net pre-tax gains (losses) on derivative contracts	(25)	48	(12)	(4)
Corporate Risk Management [Member] | Commodity Contracts [Member] | Not designated as hedges [Member]
Net pre-tax gains (losses) on derivative contracts not designated as hedges
Net pre-tax gains (losses) on derivative contracts	0	0	1	(7)
Corporate Risk Management [Member] | Not designated as hedges [Member]
Net pre-tax gains (losses) on derivative contracts not designated as hedges
Net pre-tax gains (losses) on derivative contracts	(25)	48	(11)	(11)
Foreign Exchange Contracts [Member]
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	7	2	(1)	8
Commodity Contracts [Member]
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	(5)	(118)	45	26
Other Contracts [Member]
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	$ (52)	$ 12	$ (42)	$ (5)