Revenue - Roll Forward of Frequent Flyer Deferred Revenue (Details) - Frequent Flyer - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Frequent Flyer Deferred Revenue [Roll Forward]
Total Frequent flyer deferred revenue - beginning balance	$ 6,282	$ 5,975
Total miles awarded	477	272
Travel miles redeemed	(322)	(123)
Non-travel miles redeemed	(20)	(15)
Total Frequent flyer deferred revenue - ending balance	$ 6,417	$ 6,109