Revenue Recognition - Other Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Operating revenue	$ 1,468	$ 12,536	$ 10,060	$ 23,008
Other
Disaggregation of Revenue [Line Items]
Operating revenue	682	982	1,552	2,008
Loyalty program
Disaggregation of Revenue [Line Items]
Operating revenue	269	484	743	958
Ancillary businesses and refinery
Disaggregation of Revenue [Line Items]
Operating revenue	390	330	613	699
Miscellaneous
Disaggregation of Revenue [Line Items]
Operating revenue	$ 23	$ 168	$ 196	$ 351