Carrying Values and Estimated Fair Values of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 11,326
United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	11,222
Carrying (Reported) Amount, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	11,161	12,252
Carrying (Reported) Amount, Fair Value Disclosure | United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	11,008	11,850
Estimate of Fair Value, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	12,036	13,419
Estimate of Fair Value, Fair Value Disclosure | United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	11,651	12,460
Estimate of Fair Value, Fair Value Disclosure | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	7,428	8,045
Estimate of Fair Value, Fair Value Disclosure | Level 2 | United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	7,043	7,086
Estimate of Fair Value, Fair Value Disclosure | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	4,608	5,374
Estimate of Fair Value, Fair Value Disclosure | Level 3 | United Airlines, Inc.
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 4,608	$ 5,374