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Activity for "Level Three" Financial Assets and Financial Liabilities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014 Ual And United Auction Rate Securities	Jun. 30, 2013 Ual And United Auction Rate Securities	Jun. 30, 2014 Ual And United Auction Rate Securities	Jun. 30, 2013 Ual And United Auction Rate Securities	Jun. 30, 2013 Ual And United EETC	Jun. 30, 2014 Ual And United EETC	Jun. 30, 2013 Ual And United EETC	Mar. 31, 2014 Ual And United EETC	Jun. 30, 2014 United Airlines, Inc. Convertible Debt Derivative Asset	Jun. 30, 2013 United Airlines, Inc. Convertible Debt Derivative Asset	Jun. 30, 2014 United Airlines, Inc. Convertible Debt Derivative Asset	Jun. 30, 2013 United Airlines, Inc. Convertible Debt Derivative Asset	Jun. 30, 2014 United Airlines, Inc. Convertible Debt Option Liability	Jun. 30, 2013 United Airlines, Inc. Convertible Debt Option Liability	Jun. 30, 2014 United Airlines, Inc. Convertible Debt Option Liability	Jun. 30, 2013 United Airlines, Inc. Convertible Debt Option Liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 96	$ 108	$ 105	$ 116	$ 61	$ 61	$ 63	$ 59	$ 584	$ 413	$ 480	$ 268
Purchases, (sales), issuances and (settlements) (net)	(74)		(84)	(10)		(3)	(2)		(62)		(62)
Realized	9		10	2					(5)		(5)
Unrealized				1					(68)	(18)	36	127
Reported in other comprehensive income (loss)	(5)	7	(5)	6	1	1	1
Ending Balance	26	115	26	115	62	59	62	59	449	395	449	395
Beginning Balance													(352)	(209)	(270)	(128)
Purchases, (sales), issuances and (settlements) (net)													34		34
Realized													5		5
Unrealized													50	10	(32)	(71)
Reported in other comprehensive income (loss)
Ending Balance													$ (263)	$ (199)	$ (263)	$ (199)