CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 184	$ 149
Related to marketable securities:
Unrealized holding gains (losses) arising during the period	12	7
Reclassification of (gains) losses into Other-net nonoperating income (expense)	0	0
Income tax effect	(4)	(3)
Total	8	4
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits	5	3
Income tax effect	(2)	(1)
Total	3	2
Related to interest rate derivative instruments:
Unrealized holding gains (losses) arising during the period	(5)	(4)
Reclassification of (gains) losses into Aircraft rent	1	2
Income tax effect	2	1
Total	(2)	(1)
Other Comprehensive Income	9	5
Comprehensive Income	$ 193	$ 154