Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension and Other Postretirement Plans, Net of Tax	$ (5,147)		$ (3,899)		$ (2,053)		$ (2,011)
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(286)	[1]	(413)	[1]	(312)	[1]	(345)	[1]
Accumulated Other Comprehensive Income Valuation Allowance Net Of Tax	(3,144)		(2,454)		(1,213)		(1,207)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(8,577)		(6,766)		(3,578)		(3,563)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(2,171)		(3,062)		(121)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	196	[1]	5	[1]	(71)	[1]
OtherComprehensiveIncomeValuationAllowanceChangesInFairValue	0		0		0
Accumulated Other Comprehensive Income Loss Changes In Fair Value Before Tax	(1,975)		(3,057)		(192)
Other Comprehensive Income, Reclassification of Defined Benefit Plan's Net Gain (Loss) Recognized in Net Periodic Benefit Cost, Tax	149		41		54
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax	15	[1]	(172)	[1]	123	[1]
OtherComprehensiveIncomeValuationAllowanceReclassificationToEarnings	0		0		0
Accumulated Other Comprehensive Income Loss Income Reclassification To Earnings Before Tax	164		(131)		177
Other Comprehensive Income, Defined Benefit Plans, Tax	774		1,175		25
Other Comprehensive Income, Derivatives Qualifying as Hedges, Tax Effect	(84)	[1]	66	[1]	(19)	[1]
Other Comprehensive Income Valuation Allowance Tax	690		1,241		6
Other Comprehensive Income (Loss), Tax	$ 0		$ 0		$ 0

[1] (1) Includes $321 million of deferred income tax expense that will remain in AOCI until all amounts in AOCI that relate to fuel derivatives which are designated as accounting hedges are recognized in the Consolidated Statement of Operations.