Components of Accumulated Other Comprehensive Income (loss), Net of Tax (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2012 Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2013 Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2012 Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2013 Other Accumulated Other Comprehensive Income	Sep. 30, 2012 Other Accumulated Other Comprehensive Income	Sep. 30, 2013 Other Accumulated Other Comprehensive Income	Sep. 30, 2012 Other Accumulated Other Comprehensive Income	Sep. 30, 2013 United Airlines, Inc.	Sep. 30, 2012 United Airlines, Inc.	Sep. 30, 2013 United Airlines, Inc.	Sep. 30, 2012 United Airlines, Inc.	Sep. 30, 2013 United Airlines, Inc. Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2012 United Airlines, Inc. Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2013 United Airlines, Inc. Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2012 United Airlines, Inc. Accumulated Defined Benefit Plans Adjustment	Sep. 30, 2013 United Airlines, Inc. Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2012 United Airlines, Inc. Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2013 United Airlines, Inc. Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2012 United Airlines, Inc. Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges	Sep. 30, 2013 United Airlines, Inc. Other Accumulated Other Comprehensive Income	Sep. 30, 2012 United Airlines, Inc. Other Accumulated Other Comprehensive Income	Sep. 30, 2013 United Airlines, Inc. Other Accumulated Other Comprehensive Income	Sep. 30, 2012 United Airlines, Inc. Other Accumulated Other Comprehensive Income	Sep. 30, 2013 United Airlines, Inc. Income Tax Benefit Expense	Sep. 30, 2012 United Airlines, Inc. Income Tax Benefit Expense	Jun. 30, 2012 United Airlines, Inc. Income Tax Benefit Expense	Dec. 31, 2011 United Airlines, Inc. Income Tax Benefit Expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (569)	$ (499)	$ (1,046)	$ (417)	$ (562)	$ (303)	$ (1,042)	$ (312)	$ (20)	$ (199)	$ (10)	$ (99)	$ 13	$ 3	$ 6	$ (6)	$ (569)	$ (507)	$ (1,053)	$ (425)	$ (562)	$ (303)	$ (1,042)	$ (312)	$ (20)	$ (199)	$ (10)	$ (99)	$ 13	$ 1	$ 5	$ (8)	$ (6)	$ (6)	$ (6)	$ (6)
Other comprehensive income (loss) before reclassifications	39	138	18	(22)					44	133	16	(36)	(5)	5	2	14	39	139	19	(21)					44	133	16	(36)	(5)	6	3	15
Actuarial gain due to curtailment and remeasurement	41		483		41		483										41		483		41		483
Amounts reclassified from accumulated other comprehensive income	(4)	42	52	120	10	4	48	13	(14)	38	4	107					(4)	42	58	120	10	4	48	13	(14)	38	4	107					6
Net current-period other comprehensive income (loss)	76	180	553	98	51	4	531	13	30	171	20	71	(5)	5	2	14	76	181	560	99	51	4	531	13	30	171	20	71	(5)	6	3	15	6
Ending Balance	$ (493)	$ (319)	$ (493)	$ (319)	$ (511)	$ (299)	$ (511)	$ (299)	$ 10	$ (28)	$ 10	$ (28)	$ 8	$ 8	$ 8	$ 8	$ (493)	$ (326)	$ (493)	$ (326)	$ (511)	$ (299)	$ (511)	$ (299)	$ 10	$ (28)	$ 10	$ (28)	$ 8	$ 7	$ 8	$ 7		$ (6)	$ (6)	$ (6)