Note 13 - Commitments and Contingencies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Leases, Rent Expense, Total	$ 2,328	$ 2,308	$ 2,362
Financial Grants in Support of Research and Development, Royalty Obligation	5.00%
Loss Contingency Accrual, Ending Balance	$ 10,865