Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Convertible Debt Derivative Asset | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt derivative asset	$ 712	$ 480
Convertible Debt Option Liability | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt option liability	(511)	(270)
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,002	3,220
Restricted cash	320	395
Fair Value, Measurements, Recurring | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,996	3,214
Restricted cash	320	395
Fair Value, Measurements, Recurring | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	901	694
Fair Value, Measurements, Recurring | Asset-backed Securities | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	901	694
Fair Value, Measurements, Recurring | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	876	685
Fair Value, Measurements, Recurring | Corporate Debt | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	876	685
Fair Value, Measurements, Recurring | CDARS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	256	301
Fair Value, Measurements, Recurring | CDARS | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	256	301
Fair Value, Measurements, Recurring | U.S. Government and Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	68	38
Fair Value, Measurements, Recurring | U.S. Government and Agency Notes | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	68	38
Fair Value, Measurements, Recurring | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26	105
Fair Value, Measurements, Recurring | Auction Rate Securities | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26	105
Fair Value, Measurements, Recurring | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	255	78
Fair Value, Measurements, Recurring | Other Fixed Income Securities | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	255	78
Fair Value, Measurements, Recurring | EETC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
EETC	28	61
Fair Value, Measurements, Recurring | EETC | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
EETC	28	61
Fair Value, Measurements, Recurring | Fuel derivatives asset (liability), net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	(717)	104
Fair Value, Measurements, Recurring | Fuel derivatives asset (liability), net | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	(717)	104
Fair Value, Measurements, Recurring | Foreign Currency Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	2	1
Fair Value, Measurements, Recurring | Foreign Currency Derivatives, Net | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	2	1
Fair Value, Measurements, Recurring | Convertible Debt Derivative Asset | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt derivative asset	712	480
Fair Value, Measurements, Recurring | Convertible Debt Option Liability | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt option liability	(511)	(270)
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,002	3,220
Restricted cash	320	395
Fair Value, Measurements, Recurring | Level 1 | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,996	3,214
Restricted cash	320	395
Fair Value, Measurements, Recurring | Level 2 | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	901	694
Fair Value, Measurements, Recurring | Level 2 | Asset-backed Securities | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	901	694
Fair Value, Measurements, Recurring | Level 2 | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	876	685
Fair Value, Measurements, Recurring | Level 2 | Corporate Debt | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	876	685
Fair Value, Measurements, Recurring | Level 2 | CDARS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	256	301
Fair Value, Measurements, Recurring | Level 2 | CDARS | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	256	301
Fair Value, Measurements, Recurring | Level 2 | U.S. Government and Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	68	38
Fair Value, Measurements, Recurring | Level 2 | U.S. Government and Agency Notes | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	68	38
Fair Value, Measurements, Recurring | Level 2 | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	255	78
Fair Value, Measurements, Recurring | Level 2 | Other Fixed Income Securities | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	255	78
Fair Value, Measurements, Recurring | Level 2 | Fuel derivatives asset (liability), net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	(717)	104
Fair Value, Measurements, Recurring | Level 2 | Fuel derivatives asset (liability), net | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	(717)	104
Fair Value, Measurements, Recurring | Level 2 | Foreign Currency Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	2	1
Fair Value, Measurements, Recurring | Level 2 | Foreign Currency Derivatives, Net | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, net	2	1
Fair Value, Measurements, Recurring | Level 3 | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26	105
Fair Value, Measurements, Recurring | Level 3 | Auction Rate Securities | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26	105
Fair Value, Measurements, Recurring | Level 3 | EETC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
EETC	28	61
Fair Value, Measurements, Recurring | Level 3 | EETC | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
EETC	28	61
Fair Value, Measurements, Recurring | Level 3 | Convertible Debt Derivative Asset | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt derivative asset	712	480
Fair Value, Measurements, Recurring | Level 3 | Convertible Debt Option Liability | United Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt option liability	$ (511)	$ (270)