Components of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2014 Pension and Other Postretirement Liabilities		Mar. 31, 2013 Pension and Other Postretirement Liabilities		Mar. 31, 2014 Derivative Contracts		Mar. 31, 2013 Derivative Contracts		Mar. 31, 2013 Other		Mar. 31, 2014 Other		Dec. 31, 2013 Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 608	[1]	$ (1,046)	[1]	$ 584	[1]	$ (1,042)	[1]	$ 11	[1]	$ (10)	[1]	$ 6	[1]	$ 13	[1]	$ 13	[1]
Changes in value	(15)	[1]	(11)	[1]	(5)	[1]			(10)	[1]	(9)	[1]	(2)	[1]
Amounts reclassified to earnings	(13)	[1]	30	[1]	(16)	[1]	21	[1]	3	[1]	9	[1]
Comprehensive income (loss) adjustments	(28)	[1]	19	[1]	(21)	[1]	21	[1]	(7)	[1]			(2)	[1]
Ending Balance	$ 580	[1]	$ (1,027)	[1]	$ 563	[1]	$ (1,021)	[1]	$ 4	[1]	$ (10)	[1]	$ 4	[1]	$ 13	[1]	$ 13	[1]

[1] UAL and United amounts are substantially the same except for an additional $6 million of income tax benefit at United in 2013 and additional (losses) gains related to investments and other of $1 million and $1 million in 2014 and 2013, respectively.