Components of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 580	[1]	$ (1,027)	[1]	$ 608	[1]	$ (1,046)	[1]
Changes in value	32	[1]	432	[1]	17	[1]	421	[1]
Amounts reclassified to earnings	(23)	[1]	26	[1]	(36)	[1]	56	[1]
Comprehensive income (loss) adjustments	9	[1]	458	[1]	(19)	[1]	477	[1]
Ending Balance	589	[1]	(569)	[1]	589	[1]	(569)	[1]
Pension and Other Postretirement Liabilities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	563	[1]	(1,021)	[1]	584	[1]	(1,042)	[1]
Changes in value			442	[1]	(5)	[1]	442	[1]
Amounts reclassified to earnings	(18)	[1]	17	[1]	(34)	[1]	38	[1]
Comprehensive income (loss) adjustments	(18)	[1]	459	[1]	(39)	[1]	480	[1]
Ending Balance	545	[1]	(562)	[1]	545	[1]	(562)	[1]
Derivative Contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	4	[1]	(10)	[1]	11	[1]	(10)	[1]
Changes in value	31	[1]	(19)	[1]	21	[1]	(28)	[1]
Amounts reclassified to earnings	1	[1]	9	[1]	4	[1]	18	[1]
Comprehensive income (loss) adjustments	32	[1]	(10)	[1]	25	[1]	(10)	[1]
Ending Balance	36	[1]	(20)	[1]	36	[1]	(20)	[1]
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	13	[1]	4	[1]	13	[1]	6	[1]
Changes in value	1	[1]	9	[1]	1	[1]	7	[1]
Amounts reclassified to earnings	(6)	[1]			(6)	[1]
Comprehensive income (loss) adjustments	(5)	[1]	9	[1]	(5)	[1]	7	[1]
Ending Balance	$ 8	[1]	$ 13	[1]	$ 8	[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 the six months ended June 30, 2013 and additional (losses) gains related to investments and other of $(1) million and $1 million in the three months ended June 30, 2014 and the six months ended June 30, 2013, respectively.