Financial Derivative Instruments - Offsetting Derivative Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Offsetting Liabilities
Gross amounts offset in the balance sheet	$ 4	$ 6
Fuel derivative contracts \| Prepaid expenses and other current assets
Offsetting Liabilities
Gross amounts offset in the balance sheet	80	3
Gross amounts offset in the Balance Sheet	(80)	(3)
Net amounts of liabilities presented in the Balance Sheet	0	0
Fuel derivative contracts \| Other assets
Offsetting Liabilities
Gross amounts offset in the balance sheet	95	31
Gross amounts offset in the Balance Sheet	(95)	(31)
Net amounts of liabilities presented in the Balance Sheet	0	0
Interest rate derivatives \| Other noncurrent liabilities
Offsetting Liabilities
Gross amounts offset in the balance sheet	4	6
Gross amounts offset in the Balance Sheet	0	0
Net amounts of liabilities presented in the Balance Sheet	$ 4	$ 6

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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