Financial Derivative Instruments - Fair Values by Balance Sheet Location (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Fuel derivative contracts \| Prepaid expenses and other current assets
Derivatives, Fair Value
Gross amounts of recognized assets	$ 352	$ 409
Gross amounts of recognized liabilities	106	80
Gross amounts offset in the balance sheet	106	80
Cash collateral deposits held from counterparties for fuel contracts - current	106	80
Fuel derivative contracts \| Other assets
Derivatives, Fair Value
Gross amounts of recognized assets	160	287
Gross amounts of recognized liabilities	0	95
Gross amounts offset in the balance sheet	0	95
Cash collateral deposits held from counterparties for fuel contracts - current	0	95
Fuel derivative contracts \| Accounts and other receivables
Derivatives, Fair Value
Receivable from third parties for fuel contracts	34	8
Interest rate derivatives \| Other assets
Derivatives, Fair Value
Gross amounts of recognized assets	14	0
Gross amounts of recognized liabilities	0	0
Interest rate derivatives \| Other noncurrent liabilities
Derivatives, Fair Value
Gross amounts offset in the balance sheet	0	4
Designated as Hedging Instrument
Derivatives, Fair Value
Gross amounts of recognized assets	526	696
Gross amounts offset in the balance sheet	0	4
Designated as Hedging Instrument \| Fuel derivative contracts \| Prepaid expenses and other current assets
Derivatives, Fair Value
Gross amounts of recognized assets	352	409
Designated as Hedging Instrument \| Fuel derivative contracts \| Other assets
Derivatives, Fair Value
Gross amounts of recognized assets	160	287
Designated as Hedging Instrument \| Interest rate derivatives \| Other assets
Derivatives, Fair Value
Gross amounts of recognized assets	14
Gross amounts of recognized liabilities	0
Designated as Hedging Instrument \| Interest rate derivatives \| Other noncurrent liabilities
Derivatives, Fair Value
Gross amounts offset in the balance sheet	$ 0	$ 4

Derivative, Cash Receivable (Payable) On Hedge

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Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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Fair value of liability associated with financial asset or other 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.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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