Financial Derivative Instruments - Offsetting Derivative Liabilities (Details) - Fuel derivative contracts - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Prepaid expenses and other current assets
Offsetting Liabilities [Line Items]
Gross amounts of recognized liabilities	$ 65	$ 106
Gross amounts offset in the Balance Sheet	(65)	(106)
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
Other assets
Offsetting Liabilities [Line Items]
Gross amounts of recognized liabilities	$ 11	$ 0
Gross amounts offset in the Balance Sheet	(11)	0
Net amounts of liabilities presented in the Balance Sheet	$ 0	$ 0
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets