Financial Derivative Instruments - Offsetting of Derivative Assets (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Offsetting Assets [Line Items]
Gross amounts of recognized assets	$ 579	$ 696
Fuel derivative contracts | Prepaid expenses and other current assets
Offsetting Assets [Line Items]
Gross amounts of recognized assets	397	409
Gross amounts offset in the Balance Sheet	(125)	(80)
Net amounts of assets presented in the Balance Sheet	$ 272	$ 329
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 Assets [Line Items]
Gross amounts of recognized assets	$ 168	$ 287
Gross amounts offset in the Balance Sheet	(38)	(95)
Net amounts of assets presented in the Balance Sheet	$ 130	$ 192
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Interest rate derivative contracts
Offsetting Assets [Line Items]
Net amounts of assets presented in the Balance Sheet	$ 14	$ 0
Interest rate derivative contracts | Other assets
Offsetting Assets [Line Items]
Gross amounts of recognized assets	14	0
Gross amounts offset in the Balance Sheet	$ 0	$ 0
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets