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 9 Months Ended
Jul. 10, 2020
Jul. 02, 2020
May 05, 2020
Mar. 10, 2020
Jun. 03, 2019
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 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)           14,869,000 12,007,000 14,869,000 12,007,000 11,942,000 5,941,000
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount           $ 7,920   $ 7,920      
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)               1 year 7 months 2 days      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number (in shares)           8,092,000 4,310,000 8,092,000 4,310,000    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share)           $ 4.55 $ 2.99 $ 4.55 $ 2.99    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Month)               5 years 6 months 6 years 6 months    
Share-based Payment Arrangement, Expense           $ 1,828 $ 4,905 $ 10,635 $ 17,007    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)               4,199,000 6,352,000    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares)           13,851,000 10,853,000 13,851,000 10,853,000    
Restricted Stock Units (RSUs) [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)   40,000   645,000 80,000     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                    
Restricted Stock Units (RSUs) [Member] | Share-based Payment Arrangement, Tranche One [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)         40,000            
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Month)         3 months            
Restricted Stock Units (RSUs) [Member] | Share-based Payment Arrangement, Tranche Two [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Month)     13 months   1 year            
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] | Performance Shares [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)               800,000      
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      
Officer One [Member] | Performance Shares [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)               400,000      
Officer One [Member] | Performance Shares [Member] | Share-based Payment Arrangement, Tranche One [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares)           200,000   200,000      
Officer One [Member] | Performance Shares [Member] | Share-based Payment Arrangement, Tranche Two [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares)           200,000   200,000      
Officer Two [Member] | Performance Shares [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)               400,000      
Officer Two [Member] | Performance Shares [Member] | Share-based Payment Arrangement, Tranche One [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares)           200,000   200,000      
Officer Two [Member] | Performance Shares [Member] | Share-based Payment Arrangement, Tranche Two [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares)           200,000   200,000      
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