Segments - Schedule of Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information, Profit (Loss)
Operating revenue	$ 12,560	$ 11,953	$ 35,568	$ 33,696
Operating income	2,071	1,645	5,219	4,173
Interest expense (income), net	70	73	228	244
Depreciation and amortization	631	573	1,960	1,759
Total assets, end of period	63,219	59,923	63,219	59,923	$ 60,266
Capital expenditures	946	962	3,864	3,805
Operating Segments | Airline
Segment Reporting Information, Profit (Loss)
Operating revenue	12,554	11,845	35,474	33,159
Operating income	2,022	1,633	5,167	4,072
Interest expense (income), net	70	84	247	267
Depreciation and amortization	606	557	1,886	1,711
Total assets, end of period	61,515	57,965	61,515	57,965
Capital expenditures	936	923	3,836	3,738
Operating Segments | Refinery
Segment Reporting Information, Profit (Loss)
Operating revenue	1,505	1,609	4,289	4,767
Operating income	49	12	52	101
Interest expense (income), net	0	(11)	(19)	(23)
Depreciation and amortization	25	16	74	48
Total assets, end of period	1,704	1,958	1,704	1,958
Capital expenditures	10	39	28	67
Intersegment Sales/Other
Segment Reporting Information, Profit (Loss)
Operating income	0	0	0	0
Interest expense (income), net	0	0	0	0
Depreciation and amortization	0	0	0	0
Total assets, end of period	0	0	0	0
Capital expenditures	0	0	0	0
Intersegment Sales/Other | Sales to airline segment
Segment Reporting Information, Profit (Loss)
Operating revenue	(304)	(328)	(882)	(866)
Intersegment Sales/Other | Exchanged products
Segment Reporting Information, Profit (Loss)
Operating revenue	(1,143)	(1,110)	(2,953)	(3,081)
Intersegment Sales/Other | Sales of refined products
Segment Reporting Information, Profit (Loss)
Operating revenue	$ (52)	$ (63)	$ (360)	$ (283)