Purchase Intangible Assets - (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	$ 80,049	$ 79,748
Finite-lived intangibles, Accumulated Amortization	72,263	71,116
Finite-lived intangibles, Net	7,786	8,632
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	66,127	65,827
Finite-lived intangibles, Accumulated Amortization	59,396	58,522
Finite-lived intangibles, Net	6,731	7,305
Customer and Distributor Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	9,561	9,560
Finite-lived intangibles, Accumulated Amortization	9,016	8,818
Finite-lived intangibles, Net	545	742
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	4,361	4,361
Finite-lived intangibles, Accumulated Amortization	3,851	3,776
Finite-lived intangibles, Net	$ 510	$ 585