Derivatives (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 172	$ (123)	$ (1,350)
Derivative, Gain (Loss) on Derivative, Net	(135)	136	148
Commodity Contract [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	233	(87)	(1,344)
Derivative, Gain (Loss) on Derivative, Net	187	(2)	(15)
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 420	$ (89)	$ (1,359)