Leases - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating and Capital Leases [Line Items]
Rent expense	$ 5,371,000	$ 3,753,000	$ 1,700,000
Equipment lease expense	1,926,000	1,929,000	1,813,000
Minimum [Member]
Operating and Capital Leases [Line Items]
Control Centers leases term	5 years
Control Centers leases range price	1,500
Maximum [Member]
Operating and Capital Leases [Line Items]
Control Centers leases term	10 years
Control Centers leases range price	$ 5,000