Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	$ 3,935	$ 4,770
Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	683	715
Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	581	537
CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	308	367
Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	104	116
Other Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	125	38
EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	59	63
Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivative asset (liability), net	52	46
Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	412	447
Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	3,935	4,770
Level 1 | Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	412	447
Level 2 | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	683	715
Level 2 | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	581	537
Level 2 | CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	308	367
Level 2 | Other Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	125	38
Level 2 | Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivative asset (liability), net	52	46
Level 3 | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	104	116
Level 3 | EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	59	63
United Airlines, Inc. | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	3,928	4,765
United Airlines, Inc. | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	683	715
United Airlines, Inc. | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	581	537
United Airlines, Inc. | CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	308	367
United Airlines, Inc. | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	104	116
United Airlines, Inc. | Other Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	125	38
United Airlines, Inc. | EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	59	63
United Airlines, Inc. | Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivative asset (liability), net	52	46
United Airlines, Inc. | Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	411	447
United Airlines, Inc. | Convertible Debt Derivative Asset
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Convertible debt derivative asset	376	268
United Airlines, Inc. | Convertible Debt Option Liability
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Convertible debt option liability	(185)	(128)
United Airlines, Inc. | Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	3,928	4,765
United Airlines, Inc. | Level 1 | Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	411	447
United Airlines, Inc. | Level 2 | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	683	715
United Airlines, Inc. | Level 2 | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	581	537
United Airlines, Inc. | Level 2 | CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	308	367
United Airlines, Inc. | Level 2 | Other Short-term Investments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	125	38
United Airlines, Inc. | Level 2 | Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivative asset (liability), net	52	46
United Airlines, Inc. | Level 3 | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	104	116
United Airlines, Inc. | Level 3 | EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	59	63
United Airlines, Inc. | Level 3 | Convertible Debt Derivative Asset
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Convertible debt derivative asset	376	268
United Airlines, Inc. | Level 3 | Convertible Debt Option Liability
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Convertible debt option liability	$ (185)	$ (128)