Segments - Schedule of Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information, Profit (Loss)
Operating revenue	$ 10,791	$ 10,447	$ 19,939	$ 19,698
Operating income (loss)	2,028	2,423	3,081	3,963
Interest expense, net	103	93	197	200
Depreciation and amortization	535	470	1,075	956
Total assets, end of period	51,815	51,634	51,815	51,634	$ 51,261
Capital expenditures	988	1,046	1,790	1,917
Operating Segments | Airline
Segment Reporting Information, Profit (Loss)
Operating revenue	10,724	10,398	19,811	19,570
Operating income (loss)	2,022	2,433	3,031	4,001
Interest expense, net	103	92	197	199
Depreciation and amortization	524	461	1,054	938
Total assets, end of period	50,328	50,213	50,328	50,213
Capital expenditures	928	1,026	1,704	1,884
Operating Segments | Refinery
Segment Reporting Information, Profit (Loss)
Operating revenue	1,139	1,027	2,267	1,792
Operating income (loss)	6	(10)	50	(38)
Interest expense, net	0	1	0	1
Depreciation and amortization	11	9	21	18
Total assets, end of period	1,487	1,421	1,487	1,421
Capital expenditures	60	20	86	33
Intersegment Sales/Other | Sales to airline segment
Segment Reporting Information, Profit (Loss)
Operating revenue	(193)	(178)	(383)	(322)
Intersegment Sales/Other | Exchanged products
Segment Reporting Information, Profit (Loss)
Operating revenue	(756)	(745)	(1,489)	(1,271)
Intersegment Sales/Other | Sales of refined products
Segment Reporting Information, Profit (Loss)
Operating revenue	$ (123)	$ (55)	$ (267)	$ (71)