Carrying Values and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 10,985	$ 11,434
Carrying (Reported) Amount, Fair Value Disclosure | United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	10,985	11,433
Estimate of Fair Value, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	11,388	12,386
Estimate of Fair Value, Fair Value Disclosure | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	8,573	8,568
Estimate of Fair Value, Fair Value Disclosure | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	2,815	3,818
Estimate of Fair Value, Fair Value Disclosure | United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	11,388	12,386
Estimate of Fair Value, Fair Value Disclosure | United Airlines, Inc. | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	8,573	8,568
Estimate of Fair Value, Fair Value Disclosure | United Airlines, Inc. | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,815	$ 3,818