Annual report pursuant to Section 13 and 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 13 Months Ended
Sep. 28, 2018
Jun. 29, 2018
May 30, 2018
Mar. 29, 2018
Dec. 23, 2016
Aug. 22, 2016
Dec. 31, 2018
Oct. 31, 2018
Jul. 31, 2018
Jun. 30, 2018
Apr. 30, 2018
Jan. 31, 2018
Dec. 31, 2017
Oct. 31, 2017
Sep. 30, 2017
May 31, 2017
Dec. 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2018
Jun. 08, 2018
Dec. 06, 2017
Dec. 05, 2017
Aug. 15, 2017
Aug. 14, 2017
May 19, 2017
Dec. 22, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance             4,014,475           2,694,224       4,014,475 4,014,475 2,694,224 1,909,764 4,014,475              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance             $ 4.56           $ 5.80       $ 4.56 $ 4.56 $ 5.80 $ 6.19 $ 4.56              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term                                   7 years 146 days 8 years 219 days 9 years 36 days                
Shares Issued, Price Per Share                                           $ 2.56            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross                                   2,358,559 1,000,985                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period                                   7,730                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value                                     $ 31,000                  
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                                   0.00% 0.00%                  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options             $ 4,328,328                   $ 4,328,328 $ 4,328,328     $ 4,328,328              
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition                                   2 years 262 days                    
Nonemployees [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                                   0.00% 0.00%                  
Employee Stock Option [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost     $ 97,000                                                  
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                                   0.00%                    
Restricted Stock [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                                   57,500                    
Shares Issued, Price Per Share                                                     $ 7.42  
Restricted Stock [Member] | Consultant [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                   2 years   1 year                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                   50,000   25,000                                
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                   $ 3.58   $ 5.19                                
Restricted Stock [Member] | Consultant [Member] | June 2018 [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period                                   0                    
Restricted Stock [Member] | Consultant [Member] | January 2018 [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period                                   25,000                    
The 2006 Stock Option Plan [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance             38,145                   38,145 38,145     38,145              
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant             0                   0 0     0              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance             $ 9.96                   $ 9.96 $ 9.96     $ 9.96              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term                                   1 year 109 days                    
The 2013 Plan [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance             3,976,330                   3,976,330 3,976,330     3,976,330              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance             $ 4.50                   $ 4.50 $ 4.50     $ 4.50              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term                                   7 years 182 days                    
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period                                   10 years                    
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                   4 years                    
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum                                   10.00%                    
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent                                   110.00%                    
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized, Percentage Increase of Outstanding Common Stock           4.00%                                            
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized         523,209                                              
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized         2,523,209   4,914,016                   4,914,016 4,914,016     4,914,016   4,914,016 4,000,000 4,000,000 2,523,209   2,000,000
Common Stock, Capital Shares Reserved for Future Issuance             603,712                   603,712 603,712     603,712              
The 2013 Plan [Member] | Employees [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross                                   2,146,171 981,110                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value                                   $ 2.24 $ 2.88                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period                                   0                    
The 2013 Plan [Member] | Nonemployees [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross                                   212,388 19,875                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value                                   $ 1.62 $ 4.09                  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period                                   0 0                  
The 2013 Plan [Member] | Restricted Stock [Member] | Board Members [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period             40,775 17,985 18,278   14,672 9,637   7,884 6,947 4,797                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value             $ 1.05 $ 2.48 $ 2.63   $ 3.44 $ 5.19   $ 5.55 $ 5.58 $ 7.07                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period             40,775 17,985 18,278   14,672 9,637   7,884 6,947 4,797                        
The 2013 Plan [Member] | Restricted Stock [Member] | Employees [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                         4 years                              
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period                         10,000                              
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                         $ 4.94                              
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period                                         2,500              
The 2013 Plan [Member] | Holdings Greater Than 10 Percent of Shares Outstanding [Member]                                                        
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period                                   5 years                    
2017 Employee Stock Purchase Plan [Member]                                                        
Stock Issued During Period, Shares, Employee Stock Purchase Plans 28,698 25,618   20,744                         50,727                      
Employee Stock Purchase Plan, Purchase Price $ 2.24 $ 2.31   $ 3.11     $ 0.89                   $ 0.89 $ 0.89     $ 0.89              
Employee Stock Ownership Plan (ESOP), Number of Suspense Shares             256,319                   256,319 256,319     256,319              
Shares Issued, Price Per Share             $ 0.89           $ 1.51       $ 0.89 $ 0.89 $ 1.51   $ 0.89              
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                                   0.00% 0.00%