Segments - Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information, Profit (Loss)
Operating revenue	$ 4,150	$ 8,592
Operating (loss)/income	(1,398)	(410)
Interest expense (income), net	361	79
Depreciation and amortization	492	678
Total assets, end of period	73,083	68,738	$ 71,996
Fair value obligations, end of period	(346)	(33)
Capital expenditures	438	937
Operating Segments | Airline
Segment Reporting Information, Profit (Loss)
Operating revenue	3,610	8,592
Operating (loss)/income	(1,273)	(439)
Interest expense (income), net	360	80
Depreciation and amortization	492	678
Total assets, end of period	71,505	66,864
Fair value obligations, end of period	0	0
Capital expenditures	425	926
Operating Segments | Refinery
Segment Reporting Information, Profit (Loss)
Operating revenue	1,047	1,184
Operating (loss)/income	(125)	29
Interest expense (income), net	1	(1)
Depreciation and amortization	24	25
Total assets, end of period	1,578	1,874
Fair value obligations, end of period	(346)	(33)
Capital expenditures	13	11
Intersegment Sales/Other
Segment Reporting Information, Profit (Loss)
Operating (loss)/income	0	0
Interest expense (income), net	0	0
Depreciation and amortization	(24)	(25)
Total assets, end of period	0	0
Fair value obligations, end of period	0	0
Capital expenditures	0	0
Intersegment Sales/Other | Sales to airline segment
Segment Reporting Information, Profit (Loss)
Operating revenue	0	(210)
Intersegment Sales/Other | Exchanged products
Segment Reporting Information, Profit (Loss)
Operating revenue	(503)	(831)
Intersegment Sales/Other | Sales of refined products
Segment Reporting Information, Profit (Loss)
Operating revenue	$ (4)	$ (143)