Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and amortization	$ (12,456)	$ (10,871)
Total property and equipment, net	24,375	23,039
Flight Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 28,135	26,057
Estimated useful life	20-32 years
Flight Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	32 years
Flight Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Ground Property and Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,581	5,862
Estimated useful life	3-40 years
Ground Property and Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
Ground Property and Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Flight and Ground Equipment Under Capital Lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,056	1,112
Less: accumulated depreciation and amortization	$ (757)	(782)
Estimated useful life	Shorter of lease term or estimated useful life
Advance Payments for Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,059	$ 879