Goodwill and Purchased Intangible Assets - Schedule of Purchased Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	$ 80,098	$ 79,748
Finite-lived intangibles, Accumulated Amortization	72,650	71,116
Finite-lived intangibles, Net	7,448	8,632
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Finite-lived intangibles, Gross Carrying Amount	66,177	65,827
Finite-lived intangibles, Accumulated Amortization	59,692	58,522
Finite-lived intangibles, Net	6,485	7,305
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	9,082	8,818
Finite-lived intangibles, Net	478	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	3,876	3,776
Finite-lived intangibles, Net	$ 485	$ 585