Quarterly report pursuant to Section 13 or 15(d)

Note 11 - Summary of Stock Options (Details Textual)

v3.20.1
Note 11 - Summary of Stock Options (Details Textual) - USD ($)
1 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2020
Jan. 01, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 28, 2019
Mar. 29, 2019
Jul. 31, 2019
Jun. 30, 2019
Apr. 30, 2019
Jan. 31, 2019
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Nov. 26, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares) 10,432,654   10,087,678               10,432,654   10,087,678  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share) $ 1.95   $ 2.22               $ 1.95   $ 2.22  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)                     9 years 255 days   9 years 328 days  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)                     468,000      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)                          
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                     0.00% 0.00%    
Director [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)                 525          
Stock Issued During Period, Shares, Restricted Stock Award, Gross (in shares)             378   525          
Consultant [Member]                            
Stock Issued During Period, Shares, Restricted Stock Award, Gross (in shares)               250            
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, Nonvested, Number, Ending Balance (in shares) 2,620                   2,620      
Restricted Stock [Member] | Director [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)             $ 38.08   $ 91          
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, Cost Not yet Recognized, Amount, Total $ 7,341,000                   $ 7,341,000      
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)                     3 years 36 days      
The 2006 Stock Option Plan [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares) 104                   104      
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares) 0                   0      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share) $ 992                   $ 992      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)                     2 years 292 days      
The 2013 Plan [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares) 10,432,550                   10,432,550      
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares) 4,093,287                   4,093,287      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share) $ 1.94                   $ 1.94      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)                     9 years 255 days      
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares)   2,639,926                        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)   14,512,457                       11,872,531
The 2013 Plan [Member] | Employees [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)                     368,000 21,175    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)                     $ 0.75 $ 123.66    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)                     0 0    
The 2013 Plan [Member] | Nonemployees [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)                     100,000 275    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)                     $ 1.36 $ 121.82    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)                     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 (in shares)                   3,625 0      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (in shares)                     0      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares)                     0      
2017 Employee Stock Purchase Plan [Member]                            
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares) 320   300 200 602 429                
Shares Issued, Price Per Share (in dollars per share) $ 0.59   $ 1.07 $ 3.75 $ 32.30 $ 79.88         $ 0.59   $ 1.07  
Employee Stock Ownership Plan (ESOP), Number of Suspense Shares (in shares) 772                   772      
Employee Stock Ownership Plan (ESOP), Weighted Average Purchase Price of Shares Purchased (in dollars per share)                     $ 0.43 $ 33    
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate                     0.00% 0.00%