Activity for "Level Three" Financial Assets and Financial Liabilities (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
United Airlines, Inc. \| Convertible Debt Option Liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ (270)	$ (128)
Purchases, (sales), issuances and settlements (net)	34
Realized	5
Unrealized	(280)	(142)
Reported in other comprehensive income (loss)	0	0
Ending Balance	(511)	(270)
United Airlines, Inc. \| Convertible Debt Derivative Asset
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	480	268
Purchases, (sales), issuances and settlements (net)	(62)
Realized	(5)
Unrealized	299	212
Ending Balance	712	480
UAL and United \| Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	105	116
Purchases, (sales), issuances and settlements (net)	(84)	(19)
Realized	10	3
Unrealized		1
Reported in other comprehensive income (loss)	(5)	4
Ending Balance	26	105
UAL and United \| EETC
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	61	63
Purchases, (sales), issuances and settlements (net)	(33)	(4)
Realized	1
Reported in other comprehensive income (loss)	(1)	2
Ending Balance	$ 28	$ 61

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in other comprehensive income, arising from assets, liabilities and financial instruments classified in shareholders' equity measured at fair value on a recurring basis using unobservable inputs (level 3).

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