Annual report pursuant to Section 13 and 15(d)

Note 11 - Shareholders' Equity (Details Textual)

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Note 11 - Shareholders' Equity (Details Textual) - USD ($)
 12 Months Ended
Sep. 26, 2021
Aug. 10, 2020
Feb. 13, 2020
Dec. 31, 2021
Dec. 31, 2020
Stock Issued During Period, Shares, New Issues (in shares) 7,653,060 4,600,000 2,125,000    
Shares Issued, Price Per Share (in dollars per share) $ 3.92 $ 5.00 $ 4.00    
Proceeds from Issuance of Common Stock $ 30,000,000.0 $ 23,000,000.0 $ 8,500,000 $ 29,849,000 $ 28,805,000
Proceeds from Issuance of Common Stock, Net $ 29,800,000 $ 21,100,000 $ 7,700,000    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)       40,000 14,283
Stock Issued During Period, Value, Stock Options Exercised       $ 244,000 $ 45,161
Stock Issued During Period, Shares, Exercise of Common Stock Warrants (in shares)       0  
Stock Issued During Period, Shares Settlement of Deferred Stock Units (in shares)       3,850  
Warrants Issued in Private Placement [Member]          
Stock Issued During Period, Shares, Exercise of Common Stock Warrants (in shares)         0