CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 260	$ 234	$ 444	$ 383
Related to marketable securities:
Unrealized holding gains (losses) arising during the period	7	(5)	19	2
Reclassification of (gains) losses into Other-net nonoperating income (expense)	1	0	1	0
Income tax effect	(2)	2	(6)	(1)
Total	4	(3)	12	1
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits	5	5	10	8
Income tax effect	(2)	(2)	(4)	(3)
Total	3	3	6	5
Related to interest rate derivative instruments:
Unrealized holding gains (losses) arising during the period	(2)	1	(7)	(3)
Reclassification of (gains) losses into Aircraft rent	2	1	3	3
Income tax effect	0	(1)	2	0
Total	0	1	(2)	0
Other Comprehensive Income	7	1	16	6
Comprehensive Income	$ 267	$ 235	$ 460	$ 389