Activity for "Level Three" Financial Assets and Financial Liabilities (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Ual And United | Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 116	$ 113
Purchases, (sales), issuances and settlements (net)	(19)
Realized	3
Unrealized	1	1
Reported in other comprehensive income (loss)	4	2
Ending Balance	105	116
Ual And United | EETC
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	63	60
Purchases, (sales), issuances and settlements (net)	(4)	(5)
Reported in other comprehensive income (loss)	2	8
Ending Balance	61	63
United Airlines, Inc. | Convertible Debt Derivative Asset
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	268	193
Unrealized	212	75
Ending Balance	480	268
United Airlines, Inc. | Convertible Debt Option Liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	(128)	(95)
Purchases, (sales), issuances and settlements (net)
Realized
Unrealized	(142)	(33)
Reported in other comprehensive income (loss)
Ending Balance	$ (270)	$ (128)