Components of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 608	[1]	$ (1,046)	[1]	$ (417)	[1]
Other comprehensive income (loss) before reclassifications	(1,705)	[1]	1,630	[1]	(787)	[1]
Amounts reclassified from accumulated other comprehensive income	18	[1]	24	[1]	158	[1]
Comprehensive income (loss) adjustments	(1,687)	[1]	1,654	[1]	(629)	[1]
Ending Balance	(1,079)	[1]	608	[1]	(1,046)	[1]
Pension and Other Postretirement Liabilities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	584	[1]	(1,042)	[1]	(312)	[1]
Other comprehensive income (loss) before reclassifications	(1,106)	[1],[2]	1,584	[1],[2]	(747)	[1],[2]
Amounts reclassified from accumulated other comprehensive income	(65)	[1]	42	[1]	17	[1]
Comprehensive income (loss) adjustments	(1,171)	[1]	1,626	[1]	(730)	[1]
Ending Balance	(587)	[1]	584	[1]	(1,042)	[1]
Derivative Contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	11	[1]	(10)	[1]	(100)	[1]
Other comprehensive income (loss) before reclassifications	(599)	[1]	39	[1]	(51)	[1]
Amounts reclassified from accumulated other comprehensive income	89	[1]	(18)	[1]	141	[1]
Comprehensive income (loss) adjustments	(510)	[1]	21	[1]	90	[1]
Ending Balance	(499)	[1]	11	[1]	(10)	[1]
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	13	[1]	6	[1]	(5)	[1]
Other comprehensive income (loss) before reclassifications			7	[1]	11	[1]
Amounts reclassified from accumulated other comprehensive income	(6)	[1]
Comprehensive income (loss) adjustments	(6)	[1]	7	[1]	11	[1]
Ending Balance	$ 7	[1]	$ 13	[1]	$ 6	[1]

[1] UAL and United amounts are substantially the same except for an additional $6 million of income tax benefit at United in 2013. In addition, United had additional gains related to investments and other of $1 million in both 2012 and 2013.

[2] For 2014, prior service credits increased by $3 million and actuarial losses increased by approximately $1.1 billion. For 2013, prior service credits increased by $331 million and actuarial gains increased by approximately $1.3 billion. The amount for 2012 was not material.