Derivatives and Risk Management - Not Designated Hedge Gains (Losses) (Details) - Not designated as hedges - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized	$ (75)	$ 16	$ 150	$ (29)
Foreign currency exchange contracts | Gain/(loss) on investments, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized	(7)	(3)	1	7
Fuel hedge contracts | Aircraft fuel and related taxes
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized	$ (68)	$ 19	$ 149	$ (36)