Note 9 - Income Taxes (Details Textual) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			35.00%	34.00%	34.00%
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			$ (2,378)
Deferred Tax Assets, Valuation Allowance			26,122	$ 28,500
Unrecognized Tax Benefits			3,682	$ 2,106	$ 897
Unrecognized Tax Benefits that Would Impact Effective Tax Rate			3,400
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			172
Undistributed Earnings of Foreign Subsidiaries			3,401
Accounting Standards Update 2016-09 [Member]
Deferred Tax Assets, Valuation Allowance						$ 7,849
Israel Tax Authority [Member]
Tax Credit Carryforward, Amount			$ 344
Israel Tax Authority [Member] | VSL [Member] | Earliest Tax Year [Member]
Income Tax Examination, Year under Examination	2013
Israel Tax Authority [Member] | VSL [Member] | Latest Tax Year [Member]
Income Tax Examination, Year under Examination	2015
Open Tax Year			2012
Her Majesty's Revenue and Customs (HMRC) [Member] | VSL [Member] | Latest Tax Year [Member]
Open Tax Year			2012
Ministry of the Economy, Finance and Industry, France [Member] | VSL [Member] | Latest Tax Year [Member]
Open Tax Year			2012
Domestic Tax Authority [Member]
Operating Loss Carryforwards			$ 23,992
Domestic Tax Authority [Member] | Earliest Tax Year [Member]
Open Tax Year			2012
Domestic Tax Authority [Member] | Accounting Standards Update 2016-09 [Member]
Deferred Tax Assets, Valuation Allowance						7,131
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount			$ 1,412
Domestic Tax Authority [Member] | Retention [Member]
Tax Credit Carryforward, Amount			24
Domestic Tax Authority [Member] | Foreign Tax Credit [Member]
Tax Credit Carryforward, Amount			195
State and Local Jurisdiction [Member]
Operating Loss Carryforwards			$ 10,646
State and Local Jurisdiction [Member] | Earliest Tax Year [Member]
Income Tax Examination, Year under Examination			2013
Open Tax Year			2009
State and Local Jurisdiction [Member] | Latest Tax Year [Member]
Income Tax Examination, Year under Examination			2016
State and Local Jurisdiction [Member] | Accounting Standards Update 2016-09 [Member]
Deferred Tax Assets, Valuation Allowance						$ 718
Foreign Tax Authority [Member]
Operating Loss Carryforwards			$ 534
Foreign Tax Authority [Member] | Israel Tax Authority [Member] | VSL [Member] | Minimum [Member]
Tax Rate for Amount of Dividends Distributed, Other Than Complete Liquidation			10.00%
Foreign Tax Authority [Member] | Israel Tax Authority [Member] | VSL [Member] | Maximum [Member]
Tax Rate for Amount of Dividends Distributed, Other Than Complete Liquidation			25.00%
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%