Financial Derivative Instruments - Offsetting of Derivative Assets (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Offsetting Assets [Line Items]
Gross amounts of recognized assets	$ 1,305	$ 696
Fuel derivative contracts \| Prepaid expenses and other current assets
Offsetting Assets [Line Items]
Gross amounts of recognized assets	922	409
Gross amounts offset in the Balance Sheet	(464)	(80)
Net amounts of assets presented in the Balance Sheet	458	329
Fuel derivative contracts \| Other assets
Offsetting Assets [Line Items]
Gross amounts of recognized assets	372	287
Gross amounts offset in the Balance Sheet	(162)	(95)
Net amounts of assets presented in the Balance Sheet	210	192
Interest rate derivative contracts \| Other assets
Offsetting Assets [Line Items]
Gross amounts of recognized assets	11	0
Gross amounts offset in the Balance Sheet	0	0
Net amounts of assets presented in the Balance Sheet	$ 11	$ 0

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
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
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-URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5624163-113959

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant