CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 322	$ 217	$ 588	$ 414
Related to marketable securities:
Unrealized holding gain (loss) arising during the period	4	(2)	31	(19)
Reclassification of (gain) loss into Other - net nonoperating income (expense)	(5)	2	(3)	5
Income tax effect	0	1	(7)	4
Total	(1)	1	21	(10)
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits and Other - net nonoperating income (expense)	8	7	24	21
Income tax effect	(2)	(2)	(6)	(5)
Total	6	5	18	16
Related to interest rate derivative instruments:
Unrealized holding gain (loss) arising during the period	(5)	0	(17)	8
Reclassification of loss into Aircraft rent	1	2	2	3
Income tax effect	0	(1)	3	(3)
Total	(4)	1	(12)	8
Other Comprehensive Income	1	7	27	14
Comprehensive Income	$ 323	$ 224	$ 615	$ 428