Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components Of Income Tax Expense Benefit [Line Items]
Current	$ (92)	$ 56	$ (17)
Deferred	1,648	(3,177)	13
Income tax expense (benefit)	1,556	(3,121)	(4)
United Airlines, Inc.
Components Of Income Tax Expense Benefit [Line Items]
Current	(92)	56	(17)
Deferred	1,650	(3,136)	13
Income tax expense (benefit)	$ 1,558	$ (3,080)	$ (4)