Segments - Schedule of Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information, Profit (Loss)
Operating revenue	$ 11,060	$ 10,483	$ 30,999	$ 30,181
Operating income (loss)	1,839	1,969	4,920	5,932
Interest expense, net	100	95	297	295
Depreciation and amortization	574	474	1,649	1,430
Total assets, end of period	51,928	50,948	51,928	50,948	$ 51,261
Capital expenditures	941	680	2,731	2,597
Operating Segments | Airline
Segment Reporting Information, Profit (Loss)
Operating revenue	10,931	10,473	30,742	30,043
Operating income (loss)	1,802	2,014	4,834	6,015
Interest expense, net	100	94	297	293
Depreciation and amortization	563	464	1,617	1,402
Total assets, end of period	49,992	49,748	49,992	49,748
Capital expenditures	901	652	2,605	2,536
Operating Segments | Refinery
Segment Reporting Information, Profit (Loss)
Operating revenue	1,357	971	3,624	2,763
Operating income (loss)	37	(45)	87	(83)
Interest expense, net	0	1	0	2
Depreciation and amortization	11	10	32	28
Total assets, end of period	1,936	1,200	1,936	1,200
Capital expenditures	40	28	126	61
Intersegment Sales/Other | Sales to airline segment
Segment Reporting Information, Profit (Loss)
Operating revenue	(239)	(173)	(622)	(495)
Intersegment Sales/Other | Exchanged products
Segment Reporting Information, Profit (Loss)
Operating revenue	(910)	(734)	(2,399)	(2,005)
Intersegment Sales/Other | Sales of refined products
Segment Reporting Information, Profit (Loss)
Operating revenue	$ (79)	$ (54)	$ (346)	$ (125)