Quarterly report pursuant to Section 13 or 15(d)

Note 10 - Stock-based Compensation (Details Textual)

v3.19.3
Note 10 - Stock-based Compensation (Details Textual) - USD ($)
$ in Millions
6 Months Ended 9 Months Ended
Sep. 03, 2019
Jun. 03, 2019
Jul. 13, 2018
Jun. 30, 2019
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Subscription Rate         17.50%    
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares         9,700,000    
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period         4 years    
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period         10 years    
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount         $ 1.7    
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition         1 year 237 days    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance         6,104,000   4,489,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period         80,000 150,000  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period         40,000  
Employee Stock Option Vesting Schedule I [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance         160,000 166,000  
Employee Stock Option Vesting Schedule II [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage       100.00%      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance         335,000 850,000  
Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period     90 days        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period   80,000 150,000        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period 40,000            
Share-based Payment Arrangement, Tranche One [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         50.00% 50.00%  
Share-based Payment Arrangement, Tranche One [Member] | Employee Stock Option Vesting Schedule I [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         50.00% 50.00%  
Share-based Payment Arrangement, Tranche One [Member] | Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period   90 days          
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage 50.00%            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period   40,000          
Share-based Payment Arrangement, Tranche Two [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         16.67% 16.67%  
Share-based Payment Arrangement, Tranche Two [Member] | Employee Stock Option Vesting Schedule II [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         25.00% 25.00%  
Share-based Payment Arrangement, Tranche Two [Member] | Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period   1 year          
Share-based Payment Arrangement, Tranche Three [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         16.67% 16.67%  
Share-based Payment Arrangement, Tranche Three [Member] | Employee Stock Option Vesting Schedule II [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage           25.00%  
Share-based Payment Arrangement, Tranche Three [Member] | Employee Stock Option Vesting Schedule III [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         25.00%    
Share-based Compensation Award, Tranche Four [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage         16.67% 16.67%