Annual report pursuant to Section 13 and 15(d)

Note 12 - Common Stock - Summary of Outstanding Warrants (Details)

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Note 12 - Common Stock - Summary of Outstanding Warrants (Details) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Nov. 30, 2019
Nov. 12, 2019
May 22, 2017
Shares Outstanding Under Warrants (in shares)   2,473,785      
Warrant One [Member]          
Expiration Date Feb. 17, 2025        
Exercise Price (in dollars per share) $ 4,000        
Shares Outstanding Under Warrants (in shares) 79        
Employee Performance Bonus Warrants, February 2015 Issuance [Member]          
Expiration Date   Feb. 17, 2025      
Exercise Price (in dollars per share)   $ 4,000      
Shares Outstanding Under Warrants (in shares)   79      
Warrant Two [Member]          
Expiration Date Mar. 26, 2025        
Exercise Price (in dollars per share) $ 2,720        
Shares Outstanding Under Warrants (in shares) 2        
Contractor Warrants, March 2015 Issuance [Member]          
Expiration Date   Mar. 26, 2025      
Exercise Price (in dollars per share)   $ 2,720      
Shares Outstanding Under Warrants (in shares)   2      
Warrant Three [Member]          
Expiration Date May 12, 2025        
Exercise Price (in dollars per share) $ 4,240        
Shares Outstanding Under Warrants (in shares) 37        
Contractor Warrants, May 2015 Issuance [Member]          
Expiration Date   May 12, 2025      
Exercise Price (in dollars per share)   $ 4,240      
Shares Outstanding Under Warrants (in shares)   37      
Warrant Four [Member]          
Expiration Date Dec. 16, 2025        
Exercise Price (in dollars per share) $ 5,600        
Shares Outstanding Under Warrants (in shares) 31        
May 2015 Issuance Second Contractor [Member]          
Expiration Date   May 17, 2020      
Exercise Price (in dollars per share)   $ 4,240      
Shares Outstanding Under Warrants (in shares)   22      
Warrant Five [Member]          
Expiration Date Apr. 01, 2026        
Exercise Price (in dollars per share) $ 6,080        
Shares Outstanding Under Warrants (in shares) 25        
Performance Bonus Warrants, December 2015 Issuance [Member]          
Expiration Date   Dec. 16, 2025      
Exercise Price (in dollars per share)   $ 5,600      
Shares Outstanding Under Warrants (in shares)   31      
Warrant Six [Member]          
Expiration Date May 11, 2021        
Exercise Price (in dollars per share) $ 7,740        
Shares Outstanding Under Warrants (in shares) 6        
Distributor Warrants, April 2016 Issuance [Member]          
Expiration Date   Apr. 01, 2026      
Exercise Price (in dollars per share)   $ 6,080      
Shares Outstanding Under Warrants (in shares)   25      
Warrant Seven [Member]          
Expiration Date Jun. 20, 2026        
Exercise Price (in dollars per share) $ 4,980        
Shares Outstanding Under Warrants (in shares) 101        
Contractor Warrants, May 2016 Issuance [Member]          
Expiration Date   May 11, 2021      
Exercise Price (in dollars per share)   $ 7,740      
Shares Outstanding Under Warrants (in shares)   6      
Warrant Eight [Member]          
Expiration Date May 25, 2027        
Exercise Price (in dollars per share) $ 9,500        
Shares Outstanding Under Warrants (in shares) 223        
June 2016 Issuance Related to 2016 Loan Agreement [Member]          
Expiration Date   Jun. 20, 2026      
Exercise Price (in dollars per share)   $ 4,980      
Shares Outstanding Under Warrants (in shares)   101      
Warrant Nine [Member]          
Expiration Date Nov. 26, 2024        
Exercise Price (in dollars per share) $ 6.10        
Shares Outstanding Under Warrants (in shares) 325,632        
May 2017 Issuance Related to 2017 Loan Agreement [Member]          
Expiration Date   May 25, 2027      
Exercise Price (in dollars per share)   $ 9,500     $ 9,500
Shares Outstanding Under Warrants (in shares)   223     223
Warrant Ten [Member]          
Expiration Date Nov. 26, 2024        
Exercise Price (in dollars per share) $ 18.36        
Shares Outstanding Under Warrants (in shares) 989,379        
Series A Warrants [Member]          
Expiration Date   Nov. 26, 2020      
Exercise Price (in dollars per share)   $ 18.36 $ 15.50    
Shares Outstanding Under Warrants (in shares)   989,379 741,939    
Warrant Eleven [Member]          
Expiration Date Apr. 21, 2025        
Exercise Price (in dollars per share) $ 6.37        
Shares Outstanding Under Warrants (in shares) 413,210        
Series B Warrants [Member]          
Expiration Date   Nov. 26, 2024      
Exercise Price (in dollars per share)   $ 15.50 $ 15.50    
Shares Outstanding Under Warrants (in shares) 325,632 741,940 741,939    
Warrants Issued Upon Conversion of Term Loan with CRG [Member]          
Expiration Date   Nov. 26, 2024      
Exercise Price (in dollars per share)   $ 15.50      
Shares Outstanding Under Warrants (in shares)   741,940   989,379  
Warrant Twelve [Member]          
Shares Outstanding Under Warrants (in shares) 1,728,725