Activity for "Level Three" Financial Assets and Financial Liabilities (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
Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 108	$ 112	$ 116	$ 113
Settlements			(10)
Realized			2
Reported in earnings-unrealized			1	(1)
Reported in other comprehensive income (loss)	7		6
Ending Balance	115	112	115	112
Auction Rate Securities | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	108	112	116	113
Settlements			(10)
Realized			2
Reported in earnings-unrealized			1	(1)
Reported in other comprehensive income (loss)	7		6
Ending Balance	115	112	115	112
EETC
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	61	62	63	60
Settlements			(2)	(2)
Reported in other comprehensive income (loss)	1	1	1	5
Ending Balance	62	63	62	63
EETC | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	61	62	63	60
Settlements			(2)	(2)
Reported in other comprehensive income (loss)	1	1	1	5
Ending Balance	62	63	62	63
Convertible Debt Derivative Asset | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	413	231	268	193
Reported in earnings-unrealized	(18)	58	127	96
Ending Balance	395	289	395	289
Convertible Debt Option Liability | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	(209)	(119)	(128)	(95)
Reported in earnings-unrealized	10	(28)	(71)	(52)
Ending Balance	$ (199)	$ (147)	$ (199)	$ (147)