Variable Interest Entities - Additional Information (Detail) (Variable Interest Entity, Not Primary Beneficiary)	Dec. 31, 2012 AirCraft
Mainline
Variable Interest Entity [Line Items]
Aircraft under operating lease	84
Regional Carrier
Variable Interest Entity [Line Items]
Aircraft under operating lease	256

Number of Aircraft under Operating Lease Agreements with Fixed Price Purchase Options

No definition available.

Name:	ual_NumberOfAircraftUnderOperatingLeaseAgreementsWithFixedPricePurchaseOptions
Namespace Prefix:	ual_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant