Quarterly report pursuant to Section 13 or 15(d)

Note 13 - Income Taxes (Details Textual)

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Note 13 - Income Taxes (Details Textual) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Unrecognized Tax Benefits, Ending Balance $ 0 $ 0
Domestic Tax Authority [Member]    
Operating Loss Carryforwards, Total $ 153,300  
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]    
Open Tax Year 2017 2018 2019 2020  
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member]    
Tax Credit Carryforward, Amount $ 8,900  
State and Local Jurisdiction [Member]    
Open Tax Year 2017 2018 2019 2020  
Operating Loss Carryforwards, Total $ 20,100