Revenue Recognition - Passenger 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
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	1,938	11,410	10,185	32,032
Ticket
Disaggregation of Revenue [Line Items]
Operating revenue	1,634	10,029	8,712	27,986
Loyalty travel awards
Disaggregation of Revenue [Line Items]
Operating revenue	143	732	731	2,174
Travel-related services
Disaggregation of Revenue [Line Items]
Operating revenue	$ 161	$ 649	$ 742	$ 1,872