Risk Management and Hedging Activities - Designated as Hedging Contracts (Details) (Designated as Hedging Instrument [Member], Commodity Contract [Member], USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Accumulated Other Comprehensive (Income) Loss, Net, Derivatives [Roll Forward]
Beginning balance(1)	$ 71	[1]	$ 34	[1]	$ 46	[1]	$ 37	[1]
Changes in fair value recognized in OCI	(8)		(16)		30		(14)
Net gains reclassified to operating revenue	0		1		0		1
Net losses reclassified to cost of sales	(14)		(4)		(27)		(9)
Ending balance(1)	49	[1]	15	[1]	49	[1]	15	[1]
Cash flow hedge ineffectiveness					insignificant
Cash flow hedge gain (loss) to be reclassified within twelve months					$ (33)

[1] Certain derivative contracts, principally interest rate locks, have settled and the fair value at the date of settlement remains in accumulated other comprehensive income ("AOCI") and is recognized in earnings when the forecasted transactions impact earnings.