Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	$ 3,538	$ 4,770
Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	762	715
Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	540	537
CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	399	367
Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	108	116
U.S. Government And Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	10	12
Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	33	26
EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	61	63
Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivatives, net	73	46
Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	435	447
Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	3,538	4,770
Level 1 | Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	435	447
Level 2 | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	762	715
Level 2 | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	540	537
Level 2 | CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	399	367
Level 2 | U.S. Government And Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	10	12
Level 2 | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	33	26
Level 2 | Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivatives, net	73	46
Level 3 | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	108	116
Level 3 | EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	61	63
United Airlines, Inc. | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	3,532	4,765
United Airlines, Inc. | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	762	715
United Airlines, Inc. | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	540	537
United Airlines, Inc. | CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	399	367
United Airlines, Inc. | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	108	116
United Airlines, Inc. | U.S. Government And Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	10	12
United Airlines, Inc. | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	33	26
United Airlines, Inc. | EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	61	63
United Airlines, Inc. | Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivatives, net	73	46
United Airlines, Inc. | Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	435	447
United Airlines, Inc. | Convertible Debt Derivative Asset
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Convertible debt derivative asset	413	268
United Airlines, Inc. | Convertible Debt Option Liability
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Convertible debt option liability	(209)	(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	3,532	4,765
United Airlines, Inc. | Level 1 | Restricted Cash
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Restricted cash	435	447
United Airlines, Inc. | Level 2 | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	762	715
United Airlines, Inc. | Level 2 | Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	540	537
United Airlines, Inc. | Level 2 | CDARS
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	399	367
United Airlines, Inc. | Level 2 | U.S. Government And Agency Notes
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	10	12
United Airlines, Inc. | Level 2 | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	33	26
United Airlines, Inc. | Level 2 | Fuel Derivatives, Net
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fuel derivatives, net	73	46
United Airlines, Inc. | Level 3 | Auction Rate Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	108	116
United Airlines, Inc. | Level 3 | EETC
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
EETC	61	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	413	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	$ (209)	$ (128)