Revenue - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Movement in Deferred Revenue
Air traffic liability - loyalty program - beginning balance	$ 3,385	$ 3,011
Amounts deferred associated with points awarded	656	711
Revenue recognized from points redeemed - Passenger	(461)	(535)
Revenue recognized from points redeemed - Other	(19)	(16)
Air traffic liability - loyalty program - ending balance	$ 3,561	$ 3,171