Purchase Intangible Assets - (Details) - USD ($) $ in Thousands	Jun. 30, 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	73,424	72,650
Finite-lived intangibles, Net	6,674	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	60,283	59,692
Finite-lived intangibles, Net	5,894	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	9,215	9,082
Finite-lived intangibles, Net	345	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	3,926	3,876
Finite-lived intangibles, Net	$ 435	$ 485