Annual report pursuant to Section 13 and 15(d)

Note 7 - Stockholders' Equity (Details Textual)

v3.22.1
Note 7 - Stockholders' Equity (Details Textual)
 1 Months Ended 12 Months Ended
Mar. 31, 2021
USD ($)
$ / shares
shares
Feb. 28, 2021
USD ($)
$ / shares
shares
Jan. 31, 2021
USD ($)
$ / shares
shares
Sep. 30, 2020
USD ($)
shares
Aug. 31, 2020
USD ($)
$ / shares
shares
May 31, 2020
USD ($)
$ / shares
shares
Dec. 31, 2021
USD ($)
$ / shares
shares
Dec. 31, 2020
USD ($)
$ / shares
shares
Sep. 03, 2021
USD ($)
$ / shares
Aug. 01, 2018
$ / shares
shares
Dec. 31, 2015
$ / shares
shares
Preferred Stock, Shares Authorized (in shares) | shares             10,000,000 10,000,000   10,000,000.0 5,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares             $ 0.001 $ 0.001   $ 0.001 $ 0.001
Preferred Stock, Shares Issued, Total (in shares) | shares             0 0      
Total Capital, Shares Authorized (in shares) | shares                   110,000,000.0  
Common Stock, Shares Authorized (in shares) | shares             100,000,000 100,000,000      
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares             $ 0.001 $ 0.001 $ 0.001    
Common Stock, Voting Rights Entitled             1        
Proceeds From Issuance of Common Stock, Net of Issuance Costs             $ 33,390,000 $ 14,356,000      
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) | shares     3,076,924                
Shares Issued, Price Per Share (in dollars per share) | $ / shares     $ 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) | shares   2,926,830                  
Shares Issued, Price Per Share (in dollars per share) | $ / shares   $ 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) | shares 1,512,499                    
Shares Issued, Price Per Share (in dollars per share) | $ / shares $ 9.00                    
Proceeds From Issuance of Common Stock, Net of Issuance Costs $ 13,600,000                    
Payments of Stock Issuance Costs $ 72,000                    
May 2020 Offering [Member]                      
Stock Issued During Period, Shares, New Issues (in shares) | shares           1,825,000          
Shares Issued, Price Per Share (in dollars per share) | $ / shares           $ 3.50          
Proceeds From Issuance of Common Stock, Net of Issuance Costs           $ 6,000,000.0          
May 2020 Offering [Member] | Placement Agent Fees [Member]                      
Payments of Stock Issuance Costs           319,000          
May 2020 Offering [Member] | Other Offering Expenses [Member]                      
Payments of Stock Issuance Costs           116,000          
August 2020 Offering [Member]                      
Stock Issued During Period, Shares, New Issues (in shares) | shares         4,540,541            
Shares Issued, Price Per Share (in dollars per share) | $ / shares         $ 1.85            
Proceeds From Issuance of Common Stock, Net of Issuance Costs         $ 7,600,000            
August 2020 Offering [Member] | Placement Agent Fees [Member]                      
Payments of Stock Issuance Costs         $ 588,000            
August 2020 Offering [Member] | Other Offering Expenses [Member]                      
Payments of Stock Issuance Costs           $ 180,000          
Over-Allotment Option [Member]                      
Stock Issued During Period, Shares, New Issues (in shares) | shares       448,440              
Proceeds From Issuance of Common Stock, Net of Issuance Costs       $ 771,000              
Payments of Stock Issuance Costs       $ 58,000              
Stock Issuance Program, Authorized Shares (in shares) | shares         681,081