Revenue - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Movement in Deferred Revenue
Air traffic liability - loyalty program - beginning balance	$ 3,856	$ 3,289	$ 3,385	$ 3,011
Amounts deferred associated with points awarded	447	727	1,488	2,195
Revenue recognized from points redeemed - Passenger	(205)	(657)	(747)	(1,814)
Revenue recognized from points redeemed - Other	(16)	(20)	(44)	(53)
Unused funds converted to loyalty points	105	0	105	0
Air traffic liability - loyalty program - ending balance	$ 4,187	$ 3,339	$ 4,187	$ 3,339