Debt (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 248
Less: current portion of long-term debt-United	(1,313)		(1,368)
Long-term debt, net	10,121		10,171
United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	11,533		11,604
Less: unamortized debt discount	(99)		(169)
Less: current portion of long-term debt-United	(1,313)		(1,368)
Long-term debt, net	10,120		10,020
6% convertible senior notes due 2029
Debt Instrument [Line Items]
Long-term Debt, Gross			104
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]
Long-term Debt, Gross	7,464		6,279
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]
Long-term Debt, Gross	1,151		1,243
Secured Debt | Term Loan | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	884		893
Secured Debt | Term Loan, due 2021 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	499
Secured Debt | 6.75% senior secured notes due 2015 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross			800
Unsecured Debt | Six Percent Senior Notes Due Twenty Twenty Six To Twenty Twenty Eight | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	632	[1]	652	[1]
Unsecured Debt | Senior Notes 6% Due 2020 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	300	[1]	300	[1]
Unsecured Debt | 6.375% Senior Notes due 2018 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	300	[1]	300	[1]
Unsecured Debt | 4.5% Convertible Notes Due 2015
Debt Instrument [Line Items]
Long-term Debt, Gross	202
Unsecured Debt | 4.5% Convertible Notes Due 2015 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	202		230
Unsecured Debt | 8% Notes due 2024 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross			400	[1]
Unsecured Debt | 6% Convertible Junior Subordinated Debentures due 2030 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross			248
Unsecured Debt | 4.5% Senior Limited-Subordination Convertible Notes Due 2021 | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross			156
Unsecured Debt | Other Debt | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term Debt, Gross	101		103
Adjusted For Embedded Conversion Options | United Airlines, Inc.
Debt Instrument [Line Items]
Long-term debt, net	$ 10,121	[2]	$ 10,067	[2]

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

[2] As further described below under "Convertible Debt Securities and Derivatives," there is a basis difference between UAL and United debt values, because we applied different accounting methodologies. The United debt presented above does not agree to United's balance sheet by the amount of this adjustment.