CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 262	$ 193	$ 266	$ 197
Related to marketable securities:
Unrealized holding gain (loss) arising during the period	13	(4)	27	(17)
Reclassification of (gain) loss into Other - net nonoperating income (expense)	0	1	2	3
Income tax effect	(3)	0	(7)	3
Total	10	(3)	22	(11)
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits and Other - net nonoperating income (expense)	8	7	16	14
Income tax effect	(2)	(1)	(4)	(3)
Total	6	6	12	11
Related to interest rate derivative instruments:
Unrealized holding gain (loss) arising during the period	(7)	2	(12)	8
Reclassification of (gain) loss into Aircraft rent	0	0	1	1
Income tax effect	2	0	3	(2)
Total	(5)	2	(8)	7
Other Comprehensive Income	11	5	26	7
Comprehensive Income	$ 273	$ 198	$ 292	$ 204