Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets [Line Items]
Goodwill		$ 4,523	$ 4,523
Finite-lived intangible assets, Gross Carrying Amount		1,757	1,771
Finite-lived intangible assets, Accumulated Amortization		1,313	1,234
Indefinite-lived intangible assets, Gross Carrying Amount		$ 3,095	3,095
Frequent Flyer Database
Goodwill And Intangible Assets [Line Items]
Asset life	[1],[2]	22 years
Finite-lived intangible assets, Gross Carrying Amount	[1]	$ 1,177	1,177
Finite-lived intangible assets, Accumulated Amortization	[1]	$ 832	771
Hubs
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	20 years
Finite-lived intangible assets, Gross Carrying Amount		$ 145	145
Finite-lived intangible assets, Accumulated Amortization		$ 89	82
Contracts
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	13 years
Finite-lived intangible assets, Gross Carrying Amount		$ 121	135
Finite-lived intangible assets, Accumulated Amortization		$ 103	95
Patents And Trade Names
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	3 years
Finite-lived intangible assets, Gross Carrying Amount		$ 108	108
Finite-lived intangible assets, Accumulated Amortization		$ 108	108
Airport Slots and Gates
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	8 years
Finite-lived intangible assets, Gross Carrying Amount		$ 97	97
Finite-lived intangible assets, Accumulated Amortization		$ 97	97
Other Intangible Assets
Goodwill And Intangible Assets [Line Items]
Asset life	[2]	25 years
Finite-lived intangible assets, Gross Carrying Amount		$ 109	109
Finite-lived intangible assets, Accumulated Amortization		84	81
Route Authorities
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		1,562	1,562
Airport Slots And Gates
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		536	536
Tradenames And Logos
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		593	593
Alliances
Goodwill And Intangible Assets [Line Items]
Indefinite-lived intangible assets, Gross Carrying Amount		$ 404	$ 404

[1] The frequent flyer database is amortized based on an accelerated amortization schedule to reflect utilization of the assets. Estimated cash flows correlating to the expected attrition rate of customers in the frequent flyer database is considered in the determination of the amortization schedules.

[2] Weighted average life expressed in years.