Summary of Passenger Revenue by Geographic Region and by Mainline Versus Regional (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Deferred Revenue Arrangement [Line Items]
Passenger-Mainline	$ 6,616	$ 6,227
Passenger-Regional	1,533	1,426
Total passenger revenue	8,149	7,653	[1]
International
Deferred Revenue Arrangement [Line Items]
Total passenger revenue	3,181	3,002
Domestic
Deferred Revenue Arrangement [Line Items]
Passenger-Mainline	3,485	3,272
Passenger-Regional	1,483	1,379
Total passenger revenue	4,968	4,651
Atlantic | International
Deferred Revenue Arrangement [Line Items]
Total passenger revenue	1,252	1,117
Pacific | International
Deferred Revenue Arrangement [Line Items]
Total passenger revenue	1,069	1,053
Latin America | International
Deferred Revenue Arrangement [Line Items]
Total passenger revenue	$ 860	$ 832

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.