Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible asset, Gross amount	$ 60,515	$ 52,641
Accumulated amortization	(56,454)	(49,556)
Intangible asset, Net amount	4,061	3,085
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset, Gross amount	20,194	17,903
Accumulated amortization	(20,194)	(17,903)
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset, Gross amount	29,002	25,712
Accumulated amortization	(29,002)	(25,712)
Intellectual Property Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset, Gross amount	11,319	9,026
Accumulated amortization	(7,258)	(5,941)
Intangible asset, Net amount	$ 4,061	$ 3,085