Quarterly report pursuant to Section 13 or 15(d)

Note 11 - Stock-based Compensation (Details Textual)

v3.21.2
Note 11 - Stock-based Compensation (Details Textual) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Jul. 10, 2020
May 05, 2020
Mar. 10, 2020
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares (in shares)       6,343,242   6,343,242      
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)           10 years      
Employee Stock Purchase Plan, Maximum Payroll Deduction, Percent       15.00%   15.00%      
Employee Stock Purchase Plan, Stock Purchase Price, Percent       85.00%   85.00%      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)       14,231,000 11,951,000 14,231,000 11,951,000 11,942,000 5,941,000
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount       $ 9,340   $ 9,340      
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)           1 year 8 months 23 days      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number (in shares)       8,001,000 4,190,000 8,001,000 4,190,000    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share)       $ 4.60 $ 2.97 $ 4.60 $ 2.97    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Month)           5 years 8 months 12 days 6 years 7 months 6 days    
Share-based Payment Arrangement, Expense       $ 2,164 $ 7,701 $ 8,807 $ 12,102    
Restricted Stock Units (RSUs) [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)     645,000     0 645,000    
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Month)   4 months 3 months            
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures, Total (in shares) 645,000                
Officer [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number (in shares)       1,679,169   1,679,169      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Month)           12 months      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term (Month)           12 months      
Officer [Member] | Continuing Vesting Options with No Service Requirement [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award, Accelerated Vesting, Number (in shares)           504,833      
Officer [Member] | Vested Options [Member]                  
Share-based Payment Arrangement, Expense           $ 945      
Officer [Member] | Unvested Options [Member]                  
Share-based Payment Arrangement, Expense           $ 663      
Officer [Member] | Minimum [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share)       $ 1.03   $ 1.03      
Officer [Member] | Maximum [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share)       $ 7.44   $ 7.44      
ESPP [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)       1,700,000   1,700,000      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)       0   0