Derivatives and Risk Management - Not Designated Hedge Gains (Losses) (Details) - Not designated as hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized	$ (43)	$ 49	$ 107	$ 20
Foreign currency exchange contracts | Gain/(loss) on investments, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized	(21)	18	(20)	25
Fuel hedge contracts | Aircraft fuel and related taxes
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized	$ (22)	$ 31	$ 127	$ (5)