Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits | United Continental Holdings Inc
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 25	$ 22	$ 75	$ 66
Interest cost	45	44	137	133
Expected return on plan assets	(33)	(36)	(103)	(105)
Amortization of unrecognized (gain) loss and prior service cost	4	(5)	15	(17)
Net periodic benefit costs	41	25	124	77
Pension Benefits | United Air Lines Inc
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	6	5
Interest cost	2	2	6	7
Expected return on plan assets	(2)	(3)	(8)	(8)
Amortization of unrecognized (gain) loss and prior service cost	(1)		(1)	(1)
Net periodic benefit costs	1	1	3	3
Pension Benefits | Continental Airlines Inc
Defined Benefit Plan Disclosure [Line Items]
Service cost	23	20	69	61
Interest cost	43	42	131	126
Expected return on plan assets	(31)	(33)	(95)	(97)
Amortization of unrecognized (gain) loss and prior service cost	5	(5)	16	(16)
Net periodic benefit costs	40	24	121	74
Other Postretirement Benefits | United Continental Holdings Inc
Defined Benefit Plan Disclosure [Line Items]
Service cost	11	11	37	35
Interest cost	30	32	93	95
Expected return on plan assets		(1)	(2)	(2)
Amortization of unrecognized (gain) loss and prior service cost			(2)	(1)
Net periodic benefit costs	41	42	126	127
Other Postretirement Benefits | United Air Lines Inc
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	8	26	25
Interest cost	27	29	82	85
Expected return on plan assets		(1)	(2)	(2)
Amortization of unrecognized (gain) loss and prior service cost	(1)		(3)
Net periodic benefit costs	34	36	103	108
Other Postretirement Benefits | Continental Airlines Inc
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	11	10
Interest cost	3	3	11	10
Amortization of unrecognized (gain) loss and prior service cost	1		1	(1)
Net periodic benefit costs	$ 7	$ 6	$ 23	$ 19