Fair Value Measurements and Derivative Instruments (Designated Cash Flow Hedges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative	$ 3	$ 171	$ (17)
Interest rate swaps
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative	11	165	46
Foreign currency forward contracts
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative	24	(145)	(204)
Fuel swaps
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative	$ (32)	$ 151	$ 141