Debt - Narrative (Details) $ in Millions	Mar. 31, 2023 USD ($)
Debt Instrument [Line Items]
Unamortized debt discount	$ 356
Revolving Credit Facility \| United Airlines, Inc. \| Secured Debt
Debt Instrument [Line Items]
Available under revolving credit facility	$ 1,750

Amount, after accumulated amortization, of debt discount.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant