Risk Management and Trading Activities (Details 1) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	$ (78)	$ 38	$ 52	$ 133
Corporate Risk Management [Member] | Foreign Exchange [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	(6)	(15)	13	(52)
Corporate Risk Management [Member] | Commodity [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	(8)	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	(6)	(23)	14	(59)
Foreign Exchange [Member]
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	(3)	8	(8)	6
Commodity [Member]
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	(72)	39	50	144
Other [Member]
Pre-tax gains (losses) from trading activities
Pre-tax gains (losses) from trading activities	$ (3)	$ (9)	$ 10	$ (17)