Share-Based Compensation Expense (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expense recognized in integration-related costs	$ 8	$ 4

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