Revenue Recognition - Other Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Operating revenue	$ 3,062	$ 12,560	$ 13,122	$ 35,568
Other
Disaggregation of Revenue [Line Items]
Operating revenue	982	961	2,534	2,969
Ancillary businesses and refinery
Disaggregation of Revenue [Line Items]
Operating revenue	572	291	1,185	990
Loyalty program
Disaggregation of Revenue [Line Items]
Operating revenue	343	485	1,086	1,443
Miscellaneous
Disaggregation of Revenue [Line Items]
Operating revenue	$ 67	$ 185	$ 263	$ 536