Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ (6,656)	$ (5,472)
Property, Plant and Equipment, Net	20,713	20,223
Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	21,481	21,001
Property, Plant and Equipment, Estimated Useful Lives	21-30 years
Ground Property and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,254	3,490
Property, Plant and Equipment, Estimated Useful Lives	3-40 years
Flight and Ground Equipment Under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,381	1,127
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	653	482
Property, Plant and Equipment, Estimated Useful Lives	Shorter of lease term or estimated useful life
Advance Payments for Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 253	$ 77