Schedule of Adoption of ASC 606 and Expected Impact - Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Prepaid expenses and other	$ 1,051	$ 832
Other assets:
Deferred income taxes		655
Current liabilities:
Advance ticket sales	3,876	3,730
Frequent flyer deferred revenue	2,176	2,135
Other	569	1,010
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,565	2,748
Advanced purchase of miles		430
Deferred income taxes	225
Stockholders' equity:
Retained earnings	4,621	3,427
ASC 606
Current assets:
Prepaid expenses and other	1,071	852
Other assets:
Deferred income taxes		703
Current liabilities:
Advance ticket sales	3,940	3,795
Frequent flyer deferred revenue	2,192	2,149
Other	576	1,089
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,591	2,740
Advanced purchase of miles		433
Deferred income taxes	204
Stockholders' equity:
Retained earnings	4,549	3,342
Scenario, Previously Reported | ASC 606
Current assets:
Prepaid expenses and other	1,051	832
Other assets:
Deferred income taxes		655
Current liabilities:
Advance ticket sales	3,876	3,730
Frequent flyer deferred revenue	2,176	2,135
Other	569	1,010
Other liabilities and deferred credits:
Frequent flyer deferred revenue	2,565	2,748
Advanced purchase of miles		430
Deferred income taxes	225
Stockholders' equity:
Retained earnings	4,621	3,427
Adjustment | ASC 606
Current assets:
Prepaid expenses and other	20	20
Other assets:
Deferred income taxes		48
Current liabilities:
Advance ticket sales	64	65
Frequent flyer deferred revenue	16	14
Other	7	79
Other liabilities and deferred credits:
Frequent flyer deferred revenue	26	(8)
Advanced purchase of miles		3
Deferred income taxes	(21)
Stockholders' equity:
Retained earnings	$ (72)	$ (85)