Purchase Intangible Assets - (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	$ 80,098	$ 80,098
Finite-lived intangibles, Accumulated Amortization	73,037	72,650
Finite-lived intangibles, Net	7,061	7,448
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	66,177	66,177
Finite-lived intangibles, Accumulated Amortization	59,987	59,692
Finite-lived intangibles, Net	6,190	6,485
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	9,149	9,082
Finite-lived intangibles, Net	411	478
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	4,361	4,361
Finite-lived intangibles, Accumulated Amortization	3,901	3,876
Finite-lived intangibles, Net	$ 460	$ 485