Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration of Credit Risk and Single Source Suppliers
Marketable securities	$ 25,712		$ 8,319	$ 25,712
Advertising Costs
Advertising expense			2,739	2,761	$ 2,712
Foreign Currency Translation
Foreign currency transaction gain (loss), before tax			(554)	$ (53)	$ 59
Gain on Settlement of Royalty Payments	$ 855
Accounting Standards Update 2016-09 [Member]
Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 1,571
Scenario, Forecast [Member] | Accounting Standards Update 2014-09 [Member] | Minimum
Accounting Policies [Line Items]
new accounting pronouncement effect of adoption on previously stated amounts in prior periods		$ 12,000
Revenue from Contract with Customer [Member] | Scenario, Forecast [Member] | Accounting Standards Update 2014-09 [Member] | Maximum
Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		14,000
Accumulated Earnings | Scenario, Forecast [Member] | Accounting Standards Update 2014-09 [Member] | Minimum
Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		3,000
Accumulated Earnings | Scenario, Forecast [Member] | Accounting Standards Update 2014-09 [Member] | Maximum
Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		$ 4,000