Fair Value Measurements and Derivative Instruments - Derivative Instruments, Interest Rate Risk, Foreign Currency Exchange Rate Risk (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative instruments disclosure
Maximum length of time hedged in derivative contract (in years)	3 years
Fixed interest rate on long-term debt	83.20%	75.00%
Aggregate cost of ships expected to enter service	$ 7,900
Deposit for the purchase of ships expected to enter service	$ 698
Percentage of aggregate cost exposed to fluctuations in the euro exchange rate	43.50%	52.30%
Exchange gains (losses) recorded in other income (expense)	$ (43)	$ 93	$ 24
Foreign currency forward | Not Designated as Hedging Instrument
Derivative instruments disclosure
Notional amount	1,300	1,100
Change in fair value of foreign currency forward contracts recognized in earnings	19	(102)	$ (31)
Foreign currency forward contracts
Derivative instruments disclosure
Notional amount	2,900	2,900
Interest rate swaps
Derivative instruments disclosure
Notional amount	$ 1,600	$ 1,900