Acquisitions - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Oct. 09, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Purchase price of acquired company	$ 6,300,000
Cash acquired from acquisition	2,100,000
Business combination accruals	1,100,000
Acquisition-related costs	488,000	1,306,000
Purchase price adjustment against goodwill		6,006,000	[1]
Goodwill	46,860,000	43,469,000			20,451,000	20,451,000
Maximum
Business Acquisition [Line Items]
Consideration payable based on the achievement of certain performance milestones	1,500,000
Antenna
Business Acquisition [Line Items]
Purchase price of acquired company	27,141,000			27,100,000
Acquisition-related costs	300,000	1,300,000
Purchase price adjustment against goodwill	6,000,000
Goodwill	23,018,000
Acquired identifiable intangibles	10,355,000
Acquisition-related costs, including transaction costs	$ 1,300,000

[1] The purchase price adjustments identified during 2014 have been retroactively applied as of December 31, 2013.