Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt - Additional Information (Detail)	1 Months Ended	4 Months Ended
Debt - Additional Information (Detail)	May 31, 2018	May 31, 2018 trust	Jun. 30, 2018 USD ($)
Debt Instrument [Line Items]
Number of pass-through trusts created \| trust		3
United Airlines, Inc. \| Secured Debt \| Revolving Credit Facility
Debt Instrument [Line Items]
Available under revolving credit facility \| $			$ 2,000,000,000.0
Term Loan
Debt Instrument [Line Items]
Interest rate reduction	0.25%