Annual report pursuant to Section 13 and 15(d)

Note 14 - Income Taxes (Details Textual)

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Note 14 - Income Taxes (Details Textual) - USD ($)
xbrli-pure in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Tax Expense (Benefit), Total $ 0    
Effective Income Tax Rate Reconciliation, Percent, Total 0.00% 0.00%  
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount $ 4,352,000 $ (16,506,000)  
Deferred Tax Assets, Tax Credit Carryforwards, Research 631,000 527,000  
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total 0    
Unrecognized Tax Benefits, Ending Balance 245,000 $ 223,000 $ 450,000
Domestic Tax Authority [Member]      
Operating Loss Carryforwards, Total 95,395,000    
State and Local Jurisdiction [Member]      
Operating Loss Carryforwards, Total 20,239,000    
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member]      
Deferred Tax Assets, Tax Credit Carryforwards, Research $ 817,000