Financial Derivative Instruments - Offsetting of Derivative Assets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Offsetting Assets
Gross amounts of recognized assets	$ 696	$ 134
Fuel derivative contracts \| Prepaid expenses and other current assets
Offsetting Assets
Gross amounts of recognized assets	409	13
Gross amounts of recognized liabilities	(80)	(3)
Net amounts of assets presented in the Balance Sheet	329	10
Fuel derivative contracts \| Other assets
Offsetting Assets
Gross amounts of recognized assets	287	121
Gross amounts of recognized liabilities	(95)	(31)
Net amounts of assets presented in the Balance Sheet	$ 192	$ 90

Fair value, before effects of master netting arrangements, of a 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. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant