Investments - Fair Value Investments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value Investments
Carrying value	$ 1,367	$ 1,099
Hanjin-KAL
Fair Value Investments
Ownership interest (percent)	15.00%	10.00%
Carrying value	$ 538	$ 205
Air France-KLM
Fair Value Investments
Ownership interest (percent)	9.00%	9.00%
Carrying value	$ 211	$ 418
China Eastern
Fair Value Investments
Ownership interest (percent)	3.00%	3.00%
Carrying value	$ 159	$ 258
Wheels Up
Fair Value Investments
Ownership interest (percent)	27.00%	0.00%
Carrying value	$ 234	$ 0
Other investments
Fair Value Investments
Carrying value	$ 225	$ 218