CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 4	$ 4
Related to marketable securities:
Unrealized holding gain (loss) arising during the period	14	(13)
Reclassification of (gain) loss into Other - net nonoperating income (expense)	2	2
Income tax effect	(4)	3
Total	12	(8)
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits and Other - net nonoperating income (expense)	8	7
Income tax effect	(2)	(2)
Total	6	5
Related to interest rate derivative instruments:
Unrealized holding gain (loss) arising during the period	(5)	6
Reclassification of (gain) loss into Aircraft rent	1	1
Income tax effect	1	(2)
Total	(3)	5
Other Comprehensive Income	15	2
Comprehensive Income	$ 19	$ 6