Derivatives (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Net After-tax Derivative Activity recorded in AOCI
Beginning balance-AOCI	$ 1		$ (111)
Unrealized gains (losses) recognized in AOCI	14	[1]	(25)	[1]
(Gains) Losses reclassified into income	(28)		14
Ending balance - AOCI	(13)		(122)
Commodity Contracts - cash-flow hedges
Pre-tax derivative activity
Unrealized gains (losses) recognized in AOCI	22		(40)
(Gains) losses reclassified into income	(45)		22
Losses recognized in income - ineffective portion			$ (1)

[1] Net of tax of $(8) and $14 in 2012 and 2011, respectively.