Revenue - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Movement in Deferred Revenue
Air traffic liability - loyalty program - beginning balance	$ 3,011	$ 2,667
Amounts deferred associated with points awarded	2,941	2,717
Revenue recognized from points redeemed - Passenger	(2,487)	(2,307)
Revenue recognized from points redeemed - Other	(80)	(66)
Air traffic liability - loyalty program - ending balance	$ 3,385	$ 3,011