Purchased Intangible Assets - (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	$ 79,698	$ 79,448
Finite-lived intangibles, Accumulated Amortization	70,692	69,175
Finite-lived intangibles, Net	9,006	10,273
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	65,777	65,527
Finite-lived intangibles, Accumulated Amortization	58,193	56,986
Finite-lived intangibles, Net	7,584	8,541
Customer and Distributor Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	9,560	9,560
Finite-lived intangibles, Accumulated Amortization	8,748	8,514
Finite-lived intangibles, Net	812	1,046
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	4,361	4,361
Finite-lived intangibles, Accumulated Amortization	3,751	3,675
Finite-lived intangibles, Net	$ 610	$ 686