Components of Special Charges (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating:
Severance and benefit costs	$ 23	$ 13	$ 101	$ 27
Impairment of assets	15		15	412
Labor agreement costs		14		124
Cleveland airport lease restructuring				74
(Gains) losses on sale of assets and other special charges	12	18	29	32
Special charges	50	45	145	669
Nonoperating:
Other (gain) loss				(1)
Special charges before income taxes	50	45	145	668
Income tax benefit related to special charges	(18)	(16)	(52)	(241)
Total special charges, net of tax	$ 32	$ 29	$ 93	$ 427