Quarterly report pursuant to Section 13 or 15(d)

Note 5 - Equity (Details Textual)

v3.21.2
Note 5 - Equity (Details Textual)
$ / shares in Units, $ in Thousands
1 Months Ended 6 Months Ended
Aug. 11, 2021
shares
Jun. 30, 2021
USD ($)
shares
Feb. 28, 2021
USD ($)
$ / shares
shares
Jan. 31, 2021
USD ($)
shares
Jun. 30, 2021
USD ($)
$ / shares
shares
Jun. 30, 2020
USD ($)
Proceeds from Issuance of Common Stock | $         $ 74,685 $ 15,298
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)         532,865  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares         $ 3.24  
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share) | $ / shares         $ 3.75  
The 2015 Stock Plan [Member]            
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)   43,628     43,628  
Restricted Stock Units (RSUs) [Member]            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)         150,000  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares         $ 3.73  
Share Based Compensation Arrangement by Share Based Payment Award, Number of Installment Periods   4     4  
Share-based Payment Arrangement, Option [Member] | Minimum [Member]            
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         1 year  
Share-based Payment Arrangement, Option [Member] | Maximum [Member]            
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         3 years  
The 2021 ATM Agreement [Member]            
At Market Issuance Sales Agreement, Maximum Aggregate Offering Price | $   $ 50,000     $ 50,000  
The 2021 ATM Agreement [Member] | Subsequent Event [Member]            
Stock Issued During Period, Shares, New Issues (in shares) 0          
Lincoln Park Transaction [Member]            
Purchase Agreement, Common Stock, Maximum Aggregate Commitment | $   $ 20,000     $ 20,000  
Stock Issued During Period, Shares, Commitment Consideration (in shares)   107,788        
Purchase Agreement, Maximum Aggregate Commitment, Number of Additional Shares Issued (in shares)   53,893     53,893  
Stock Issued During Period, Value, Additional Commitment Shares | $         $ 400  
February 2021 Stock Offering [Member]            
Stock Issued During Period, Shares, New Issues (in shares)     14,273,684      
Shares Issued, Price Per Share (in dollars per share) | $ / shares     $ 4.75      
Proceeds from Issuance of Common Stock | $     $ 78,000      
Over-Allotment Option [Member]            
Stock Issued During Period, Shares, New Issues (in shares)     2,141,052      
The 2020 ATM Agreement [Member]            
Stock Issued During Period, Shares, New Issues (in shares)       468,684    
Proceeds from Issuance of Common Stock | $       $ 2,900