Quarterly report pursuant to Section 13 or 15(d)

Note 10 - Summary of Stock Options (Details Textual)

v3.19.1
Note 10 - Summary of Stock Options (Details Textual) - USD ($)
1 Months Ended 3 Months Ended 12 Months Ended
Mar. 29, 2019
Jan. 01, 2019
Mar. 31, 2019
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Jun. 08, 2018
Dec. 06, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance     5,593,130 5,593,130   4,014,475    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance     $ 3.28 $ 3.28   $ 4.56    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term       8 years 73 days   7 years 146 days    
Shares Issued, Price Per Share     $ 0.91 $ 0.91     $ 2.56  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross       2,145,000        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period              
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate       0.00% 0.00%      
Nonemployees [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate       0.00% 0.00%      
Restricted Stock [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period     1,800          
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period       0        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance     419,147 419,147        
Share-based Payment Arrangement, Option [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate       0.00%        
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount     $ 4,607,000 $ 4,607,000        
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition       2 years 219 days        
The 2006 Stock Option Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance     10,434 10,434        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant     0 0        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance     $ 10.05 $ 10.05        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term       3 years 306 days        
The 2013 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance     5,582,696 5,582,696        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance     $ 3.26 $ 3.26        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term       8 years 73 days        
Common Stock, Capital Shares Reserved for Future Issuance     678,216 678,216        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized   2,043,142            
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized   6,957,158           4,914,016
The 2013 Plan [Member] | Employees [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross       2,117,500 1,251,171      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value       $ 1.24 $ 2.77      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period         0 0    
The 2013 Plan [Member] | Nonemployees [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross       27,500 2,388      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value       $ 1.22 $ 2.98      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period       0 0      
The 2013 Plan [Member] | Restricted Stock [Member]                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period       364,072        
2017 Employee Stock Purchase Plan [Member]                
Stock Issued During Period, Shares, Employee Stock Purchase Plans 43,759              
Employee Stock Purchase Plan, Purchase Price $ 0.80              
Employee Stock Ownership Plan (ESOP), Number of Suspense Shares     212,560 212,560        
Shares Issued, Price Per Share     $ 0.33 $ 0.33 $ 1.30      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate       0.00% 0.00%