Annual report pursuant to Section 13 and 15(d)

Note 11 - Income Taxes (Details Textual)

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Note 11 - Income Taxes (Details Textual) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Expense (Benefit), Total $ 0    
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount 11,667,000 $ 1,501,000  
Deferred Tax Assets, Tax Credit Carryforwards, Research 951,000 835,000  
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total 0    
Unrecognized Tax Benefits, Ending Balance $ 450,000 $ 397,000 $ 268,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent 21.00% 34.00%  
Domestic Tax Authority [Member]      
Operating Loss Carryforwards, Total $ 126,893,000    
Deferred Tax Assets, Tax Credit Carryforwards, Research 830,000    
State and Local Jurisdiction [Member]      
Operating Loss Carryforwards, Total 97,677,000    
Deferred Tax Assets, Tax Credit Carryforwards, Research $ 668,000