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Activity for "Level Three" Financial Assets and Financial Liabilities (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Auction Rate Securities
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance $ 113 $ 119
Settlements   (10)
Gains reported in earnings 1 3
Reported in other comprehensive income (loss) 2 1
Ending Balance 116 113
Auction Rate Securities | United Airlines, Inc.
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 113 119
Purchases, sales, issuances and settlements (net)   (10)
Realized   1
Unrealized 1 2
Reported in other comprehensive income (loss) 2 1
Ending Balance 116 113
EETC
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 60 66
Settlements (5) (4)
Reported in other comprehensive income (loss) 8 (2)
Ending Balance 63 60
EETC | United Airlines, Inc.
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 60 66
Purchases, sales, issuances and settlements (net) (5) (4)
Reported in other comprehensive income (loss) 8 (2)
Ending Balance 63 60
Convertible Debt Derivative Asset | United Airlines, Inc.
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 193 286
Unrealized 75 (93)
Ending Balance 268 193
Convertible Debt Option Liability | United Airlines, Inc.
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance (95) (164)
Unrealized (33) 69
Ending Balance $ (128) $ (95)