Debt (Parenthetical) (Detail)	12 Months Ended				1 Months Ended	3 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Jan. 31, 2014	Mar. 31, 2014	Sep. 30, 2014	Nov. 30, 2013	May 31, 2013	Oct. 10, 2014
Senior Notes 6% Due 2020
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%
6.375% Senior Notes due 2018
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.375%
4.5% Convertible Notes Due 2015
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.50%
6% Convertible Junior Subordinated Debentures due 2030
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%
Debt instrument, maturity date	2030
6% convertible senior notes due 2029
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%		6.00%
Debt instrument, maturity date	2029		2029
Secured Debt | Notes payable, fixed interest rates of 1.42% to 12.00% (weighted average rate of 5.88% as of December 31, 2014), payable through 2026 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate, minimum	1.42%		1.42%
Debt instrument stated interest rate, maximum	12.00%		12.00%
Weighted average interest rate	5.86%		5.86%
Debt instrument, maturity date	2026		2026
Secured Debt | Notes payable, floating interest rates of the London Interbank Offered Rate ("LIBOR") plus 0.20% to 5.46%, payable through 2026 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument, maturity date	2026		2026
Secured Debt | Term Loan | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument, maturity date	2019		2019
Secured Debt | Term Loan | United Airlines, Inc. | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.75%		2.75%
Secured Debt | Term Loan | United Airlines, Inc. | Interest Rate Floor
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.75%		0.75%
Secured Debt | Term Loan | United Airlines, Inc. | Certain Market Interest Rates
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.75%		1.75%
Secured Debt | Term Loan, due 2021 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument, maturity date	2021		2021
Secured Debt | Term Loan, due 2021 | United Airlines, Inc. | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.00%		3.00%
Secured Debt | Term Loan, due 2021 | United Airlines, Inc. | Interest Rate Floor
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.75%		0.75%
Secured Debt | Term Loan, due 2021 | United Airlines, Inc. | Certain Market Interest Rates
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%		2.00%
Secured Debt | 6.75% senior secured notes due 2015 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.75%		6.75%				6.75%
Debt instrument, maturity date	2015		2015
Unsecured Debt
Debt Instrument [Line Items]
Debt instrument stated interest rate					4.50%
Debt instrument, maturity date					2021
Unsecured Debt | Six Percent Senior Notes Due Twenty Twenty Six To Twenty Twenty Eight | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%	[1]	6.00%	[1]
Unsecured Debt | Senior Notes 6% Due 2020
Debt Instrument [Line Items]
Debt instrument stated interest rate								6.00%
Unsecured Debt | Senior Notes 6% Due 2020 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%	[1]	6.00%	[1]
Debt instrument, maturity date	2020	[1]	2020	[1]
Unsecured Debt | 6.375% Senior Notes due 2018
Debt Instrument [Line Items]
Debt instrument stated interest rate									6.375%
Unsecured Debt | 6.375% Senior Notes due 2018 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.375%	[1]	6.375%	[1]
Debt instrument, maturity date	2018	[1]	2018	[1]
Unsecured Debt | 4.5% Convertible Notes Due 2015
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.50%
Debt instrument, maturity date	2015
Unsecured Debt | 4.5% Convertible Notes Due 2015 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.50%		4.50%
Debt instrument, maturity date	2015		2015
Unsecured Debt | 8% Notes due 2024 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	8.00%	[1]	8.00%	[1]
Debt instrument, maturity date	2024	[1]	2024	[1]
Unsecured Debt | 6% Convertible Junior Subordinated Debentures due 2030 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	6.00%		6.00%							6.00%
Debt instrument, maturity date	2030		2030
Unsecured Debt | 4.5% Senior Limited-Subordination Convertible Notes Due 2021
Debt Instrument [Line Items]
Debt instrument stated interest rate						4.50%
Debt instrument, maturity date						2021
Unsecured Debt | 4.5% Senior Limited-Subordination Convertible Notes Due 2021 | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.50%	[1]	4.50%	[1]
Debt instrument, maturity date	2021	[1]	2021	[1]
Minimum | Secured Debt | Notes payable, floating interest rates of the London Interbank Offered Rate ("LIBOR") plus 0.20% to 5.46%, payable through 2026 | United Airlines, Inc. | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.20%		0.20%
Minimum | Unsecured Debt | Six Percent Senior Notes Due Twenty Twenty Six To Twenty Twenty Eight | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument, maturity date	2026	[1]	2026	[1]
Maximum | Secured Debt | Notes payable, floating interest rates of the London Interbank Offered Rate ("LIBOR") plus 0.20% to 5.46%, payable through 2026 | United Airlines, Inc. | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	5.46%		5.46%
Maximum | Unsecured Debt | Six Percent Senior Notes Due Twenty Twenty Six To Twenty Twenty Eight | United Airlines, Inc.
Debt Instrument [Line Items]
Debt instrument, maturity date	2028	[1]	2028	[1]

[1] UAL is the issuer of this debt. United is a guarantor.