Components of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) - Entity [Domain] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (977)	$ 580	$ (1,079)	$ 608
Changes in value	[1]	39	32	(29)	17
Amounts reclassified to earnings	[1]	126	(23)	296	(36)
Comprehensive income (loss) adjustments	[1]	165	9	267	(19)
Ending Balance	[1]	(812)	589	(812)	589
Pension and Other Postretirement Liabilities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(585)	563	(587)	584
Changes in value	[1]	20		12	(5)
Amounts reclassified to earnings	[1]	8	(18)	18	(34)
Comprehensive income (loss) adjustments	[1]	28	(18)	30	(39)
Ending Balance	[1]	(557)	545	(557)	545
Derivative Contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(413)	4	(499)	11
Changes in value	[1]	29	31	(46)	21
Amounts reclassified to earnings	[1]	118	1	279	4
Comprehensive income (loss) adjustments	[1]	147	32	233	25
Ending Balance	[1]	(266)	36	(266)	36
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	21	13	7	13
Changes in value	[1]	(10)	1	5	1
Amounts reclassified to earnings	[1]		(6)	(1)	(6)
Comprehensive income (loss) adjustments	[1]	(10)	(5)	4	(5)
Ending Balance	[1]	$ 11	$ 8	$ 11	$ 8

[1] UAL and United amounts are substantially the same except for additional gains (losses) related to investments and other of $1 million at United in the three and six months ended June 30, 2015 and $(1) million at United for the three months ended June 30, 2014.