Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended			3 Months Ended		0 Months Ended		3 Months Ended		0 Months Ended		9 Months Ended				9 Months Ended		3 Months Ended	0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014 Unsecured Debt	Jan. 10, 2014 Unsecured Debt	Sep. 30, 2014 Revolving Credit Facility	Sep. 30, 2014 Revolving Credit Facility Before Amendment	Sep. 30, 2014 Revolving Credit Facility After Amendment	Jun. 30, 2014 4.5% Convertible Notes Due 2015	Sep. 30, 2014 4.5% Convertible Notes Due 2015	Jan. 17, 2014 8% notes due 2024	Jan. 17, 2014 8% notes due 2024	Mar. 31, 2014 6% Convertible Senior Notes	Sep. 30, 2014 6% Convertible Senior Notes	Oct. 23, 2014 6% Convertible Senior Notes Subsequent Event	Oct. 23, 2014 6% Convertible Senior Notes Subsequent Event	Sep. 30, 2014 6% convertible junior subordinated debentures due 2030	Sep. 30, 2014 United Airlines, Inc.	Sep. 30, 2014 United Airlines, Inc. Term Loan Facility	Mar. 27, 2013 United Airlines, Inc. Term Loan Facility	Sep. 30, 2014 United Airlines, Inc. Term Loan Facility LIBOR	Sep. 30, 2014 United Airlines, Inc. 6.75% senior secured notes due 2015	Dec. 31, 2014 United Airlines, Inc. 6% convertible junior subordinated debentures due 2030 Scenario Forecast	Oct. 10, 2014 United Airlines, Inc. 6% convertible junior subordinated debentures due 2030 Subsequent Event	Oct. 10, 2014 United Airlines, Inc. 6% convertible junior subordinated debentures due 2030 Subsequent Event
Debt Instrument [Line Items]
Debt purchased and retired								$ 28													$ 800	$ 65	$ 248
Outstanding balance of debt instrument									202				58		58
Debt instrument stated interest rate			4.50%	4.50%				4.50%	4.50%		8.00%	6.00%				6.00%					6.75%			6.00%
Common stock issued in exchange for convertible notes			5.0									5.0		6.7
Aggregate principal amount of convertible senior notes exchanged	202	240	156									46					156
Debt instrument maturity year			2021					2015		2024		2029				2030
Debt instrument conversion rate			30.6419											115.1013
Note redemption date														2014-11
Aggregate principal amount of debt redeemed											400
Credit Agreement					1,315	1,000	1,350											500	900
Debt instrument maturity date																		2021-09
Debt instrument, basis spread on variable rate																				3.00%
Credit facility outstanding amount																		$ 887
Debt instrument, maturity date					Jan. 02, 2019