Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Residual Travel Funds	15.00%		15.00%		28.00%	2.00%
Remaining customer travel funds	$ 1,500		$ 1,500
Loyalty points, redemption period			2 years
Total operating revenues	4,008	$ 1,008	$ 6,060	$ 5,242
Chase Bank USA Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total operating revenues	$ 352	$ 256	$ 632	$ 577