Quarterly report pursuant to Section 13 or 15(d)

Note 6 - Stockholders' Equity (Details Textual)

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Note 6 - Stockholders' Equity (Details Textual) - USD ($)
 1 Months Ended 3 Months Ended
Mar. 25, 2022
Mar. 31, 2021
Feb. 28, 2021
Jan. 31, 2021
Mar. 31, 2022
Mar. 31, 2021
Sep. 03, 2021
Proceeds From Issuance of Common Stock, Net of Issuance Costs         $ 0 $ 33,399,000  
Common Stock, Maximum Amount to Be Distributed Through Financial Institutions             $ 75,000,000
Financial Institutions, Commission Rate             3.00%
January 2021 Offering [Member]              
Stock Issued During Period, Shares, New Issues (in shares)       3,076,924      
Shares Issued, Price Per Share (in dollars per share)       $ 2.60      
Proceeds From Issuance of Common Stock, Net of Issuance Costs       $ 8,000,000.0      
Payments of Stock Issuance Costs       $ 73,000      
February 2021 Offering [Member]              
Stock Issued During Period, Shares, New Issues (in shares)     2,926,830        
Shares Issued, Price Per Share (in dollars per share)     $ 4.10        
Proceeds From Issuance of Common Stock, Net of Issuance Costs     $ 12,000,000.0        
Payments of Stock Issuance Costs     $ 70,000        
March 2021 Offering [Member]              
Stock Issued During Period, Shares, New Issues (in shares)   1,512,499          
Shares Issued, Price Per Share (in dollars per share)   $ 9.00       $ 9.00  
Proceeds From Issuance of Common Stock, Net of Issuance Costs   $ 13,600,000          
Payments of Stock Issuance Costs   $ 72,000          
Tumim [Member]              
Common Stock, Maximum Shares Sold (in shares) 10,000,000            
Tumim [Member] | Purchase Agreement [Member]              
Stock Issued During Period, Shares, New Issues (in shares) 50,000            
Stock Issued During Period, Value, New Issues $ 100,000            
Common Stock, Maximum Shares Allowed to Issue and Sell, Initial (in shares) 7,361,833            
Common Stock, Maximum Shares Allowed to Issue and Sell, Percentage of Shares Issued and Outstanding, Initial 19.99%            
Common Stock, Price Per Share, Percentage of Weighted Average Price 95.00%            
Tumim [Member] | Purchase Agreement [Member] | Minimum [Member]              
Beneficial Ownership, Minimum Percentage of Shares Outstanding, Initial 4.99%            
Tumim [Member] | Purchase Agreement [Member] | Maximum [Member]              
Beneficial Ownership, Minimum Percentage of Shares Outstanding, Initial 9.99%