CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 256	$ 274	$ 700	$ 657
Related to marketable securities:
Unrealized holding gains (losses) arising during the period	(2)	0	17	2
Reclassification of (gains) losses into Other-net nonoperating income (expense)	0	0	1	0
Income tax effect	0	0	(6)	(1)
Total	(2)	0	10	1
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits	5	3	15	11
Income tax effect	(1)	(1)	(5)	(4)
Total	4	2	10	7
Related to interest rate derivative instruments:
Unrealized holding gains (losses) arising during the period	1	(5)	(6)	(8)
Reclassification of (gains) losses into Aircraft rent	1	2	4	5
Income tax effect	(1)	2	1	2
Total	1	(1)	(1)	(1)
Other Comprehensive Income	3	1	19	7
Comprehensive Income	$ 259	$ 275	$ 719	$ 664