Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended	1 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2012	Jan. 31, 2014	Dec. 31, 2014	Oct. 10, 2014	Dec. 31, 2013	Jan. 31, 2015
Fair Value [Line Items]
Debt purchased and retired	$ 212
Unsecured Debt
Fair Value [Line Items]
Debt instrument convertible stated interest rate		4.50%
Debt instrument maturity year		2021
Debt instument converted amount		156
Asset-backed Securities | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			1 year
Asset-backed Securities | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			40 years
Corporate Debt | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			1 year
Corporate Debt | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			6 years
CDARS | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			1 year
U.S. Government and Other Securities | Minimum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			1 year
U.S. Government and Other Securities | Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities			4 years
6% Convertible Junior Subordinated Debentures due 2030
Fair Value [Line Items]
Debt instrument convertible stated interest rate			6.00%
Debt instrument maturity year			2030
6% Convertible Junior Subordinated Debentures due 2030 | United Airlines, Inc. | Unsecured Debt
Fair Value [Line Items]
Debt instrument convertible stated interest rate			6.00%	6.00%	6.00%
Debt instrument maturity year			2030		2030
Debt purchased and retired				248
4.5% Convertible Notes Due 2015
Fair Value [Line Items]
Debt instrument convertible stated interest rate			4.50%
4.5% Convertible Notes Due 2015 | Unsecured Debt
Fair Value [Line Items]
Debt instrument convertible stated interest rate			4.50%
Debt instrument maturity year			2015
Debt purchased and retired			28
4.5% Convertible Notes Due 2015 | Subsequent Event | Unsecured Debt
Fair Value [Line Items]
Debt instrument convertible stated interest rate						4.50%
Debt instument converted amount						$ 202
4.5% Convertible Notes Due 2015 | United Airlines, Inc. | Unsecured Debt
Fair Value [Line Items]
Debt instrument convertible stated interest rate			4.50%		4.50%
Debt instrument maturity year			2015		2015