Segments - Schedule of Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information, Profit (Loss)
Operating revenue	$ 8,592	$ 10,472
Operating income (loss)	(410)	1,020
Interest expense (income), net	79	83
Depreciation and amortization	678	615
Total assets, end of period	68,738	61,841	$ 64,532
Capital expenditures	937	1,360
Operating Segments | Airline
Segment Reporting Information, Profit (Loss)
Operating revenue	8,592	10,424
Operating income (loss)	(439)	1,054
Interest expense (income), net	80	92
Depreciation and amortization	678	615
Total assets, end of period	66,864	60,343
Capital expenditures	926	1,350
Operating Segments | Refinery
Segment Reporting Information, Profit (Loss)
Operating revenue	1,184	1,283
Operating income (loss)	29	(34)
Interest expense (income), net	(1)	(9)
Depreciation and amortization	25	23
Total assets, end of period	1,874	1,498
Capital expenditures	11	10
Intersegment Sales/Other
Segment Reporting Information, Profit (Loss)
Operating income (loss)	0	0
Interest expense (income), net	0	0
Depreciation and amortization	(25)	(23)
Total assets, end of period	0	0
Capital expenditures	0	0
Intersegment Sales/Other | Sales to airline segment
Segment Reporting Information, Profit (Loss)
Operating revenue	(210)	(271)
Intersegment Sales/Other | Exchanged products
Segment Reporting Information, Profit (Loss)
Operating revenue	(831)	(732)
Intersegment Sales/Other | Sales of refined products
Segment Reporting Information, Profit (Loss)
Operating revenue	$ (143)	$ (232)