Revenue Recognition - Other Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Operating revenue	$ 17,095	$ 47,007	$ 44,438
Other
Disaggregation of Revenue [Line Items]
Operating revenue	3,604	3,977	3,818
Ancillary businesses and refinery
Disaggregation of Revenue [Line Items]
Operating revenue	1,798	1,297	1,801
Loyalty program
Disaggregation of Revenue [Line Items]
Operating revenue	1,458	1,962	1,459
Miscellaneous
Disaggregation of Revenue [Line Items]
Operating revenue	$ 348	$ 718	$ 558