Note 2 - Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Ending Balance	$ 335	$ 327
Other than Temporary Impairment Losses, Investments, Total	0	0	$ 0
Inventory, Net, Total	7,464	9,819	9,422
Inventory Valuation Reserves, Ending Balance	382	508	468
Impairment of Long-Lived Assets Held-for-use	0	0	0
Capitalized Computer Software, Additions	0	0	0
Goodwill, Impairment Loss	0	0	0
Severance Costs	1,685	1,679	1,666
Financial Grants in Support of Research and Development	$ 1,635	$ 1,678	$ 1,528
Financial Grants in Support of Research and Development, Royalty Obligation	5.00%
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,419,612	1,317,197	1,378,282
Debt Securities, Available-for-sale, Amortized Cost, Total	$ 87,024	$ 99,406
Debt Securities, Available-for-sale, Total	86,958	97,772
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain (Loss), before Tax, Total	66
Accounts Receivable, Allowance for Credit Loss, Ending Balance	0	0
Operating Lease, Right-of-Use Asset	11,655
Operating Lease, Liability, Total	13,005
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset				$ 12,500
Operating Lease, Liability, Total				$ 12,500
Foreign Exchange Option [Member]
Price Risk Cash Flow Hedge Asset, at Fair Value	$ 0	$ 3,600	$ 0
Minimum [Member]
Finite-Lived Intangible Asset, Useful Life	5 years
Derivative Instrument Hedging Period	30 days
Maximum [Member]
Finite-Lived Intangible Asset, Useful Life	6 years
Derivative Instrument Hedging Period	1 year