Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jan. 01, 2022 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Maximum length of time hedged in derivative contract (in years)	3 years
Number of operating segments | segment	1
Accounting Standards Update [Extensible Enumeration]			Accounting Standards Update 2020-06 [Member]
Accumulated deficit	$ (10)	$ (1,707)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt				$ 162
Decrease to additional paid in capital				308
Accumulated deficit				$ 146
Media advertising
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Advertising costs	379	380	$ 303
Brochure, production and direct mail costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Advertising costs	$ 127	$ 129	$ 89
Ships | Lower Limit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	30 years
Residual value, percentage	10.00%
Drydock services period	30 months
Ships | Upper Limit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	35 years
Residual value, percentage	15.00%
Drydock services period	60 months