Activity for "Level Three" Financial Assets and Financial Liabilities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 116	$ 113
Settlements	(10)
Realized	2
Reported in earnings-unrealized	1	(1)
Reported in other comprehensive income (loss)	(1)
Ending Balance	108	112
Auction Rate Securities | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	116	113
Purchases, sales, issuances and settlements (net)	(10)
Realized	2
Unrealized	1	(1)
Reported in other comprehensive income (loss)	(1)
Ending Balance	108	112
EETC
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	63	60
Settlements	(2)	(2)
Reported in other comprehensive income (loss)		4
Ending Balance	61	62
EETC | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	63	60
Purchases, sales, issuances and settlements (net)	(2)	(2)
Reported in other comprehensive income (loss)		4
Ending Balance	61	62
Convertible Debt Derivative Asset | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	268	193
Unrealized	145	38
Ending Balance	413	231
Convertible Debt Option Liability | United Airlines, Inc.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	(128)	(95)
Unrealized	(81)	(24)
Ending Balance	$ (209)	$ (119)