Share-Based Compensation Expense (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expense recognized in integration-related costs	$ 3	$ 3	$ 11	$ 7

Share Based Expense Recognized In integration Related Costs

No definition available.

Name:	ual_ShareBasedExpenseRecognizedInIntegrationRelatedCosts
Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration