Financial Derivative Instruments - Offsetting Derivative Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Offsetting Liabilities [Line Items]
Gross amounts of recognized liabilities	$ 23	$ 0
Fuel derivative contracts | Prepaid expenses and other current assets
Offsetting Liabilities [Line Items]
Gross amounts of recognized liabilities	41	15
Gross amounts offset in the Balance Sheet	(41)	(15)
Net amounts of liabilities presented in the Balance Sheet	$ 0	$ 0
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Prepaid expenses and other current assets	Prepaid expenses and other current assets
Fuel derivative contracts | Other assets
Offsetting Liabilities [Line Items]
Gross amounts of recognized liabilities	$ 32	$ 35
Gross amounts offset in the Balance Sheet	(32)	(35)
Net amounts of liabilities presented in the Balance Sheet	$ 0	$ 0
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets