Revenue Recognition - Loyalty Program Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loyalty Program
Miles earned	$ 2,238	$ 1,437	$ 3,156
Travel miles redeemed	(1,786)	(935)	(2,900)
Non-travel miles redeemed	(75)	(48)	(169)
Loyalty program
Loyalty Program
Current and noncurrent deferred revenue, beginning	7,182	6,728	6,641
Current and noncurrent deferred revenue, ending	$ 7,559	$ 7,182	$ 6,728