Quarterly report pursuant to Section 13 or 15(d)

Note 10 - Stock-based Compensation - Stock Options Activity (Details)

v3.19.2
Note 10 - Stock-based Compensation - Stock Options Activity (Details) - $ / shares
 6 Months Ended 12 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Dec. 31, 2017
Granted, Number of Shares (in shares) 62,944    
Share-based Payment Arrangement, Option [Member]      
Outstanding, Number of Shares (in shares) 986,691 1,003,916  
Outstanding, Weighted Average Exercise Price (in dollars per share) $ 4.72 $ 4.18  
Outstanding, Weighted Average Fair Value (in dollars per share) $ 2.25 $ 2.09 $ 1.87
Outstanding, Weighted Average Remaining Contractual Life (Year) 6 years 73 days 6 years 292 days 8 years 36 days
Granted, Number of Shares (in shares) 62,944 145,792  
Granted, Weighted Average Exercise Price (in dollars per share) $ 12.02 $ 7  
Exercised, Number of Shares (in shares) (47,804) (95,162)  
Exercised, Weighted Average Exercise Price (in dollars per share) $ 5.01 $ 3.48  
Cancelled, Number of Shares (in shares) (67,855)  
Cancelled, Weighted Average Exercise Price (in dollars per share) $ 3.37  
Outstanding, Number of Shares (in shares) 1,001,831 986,691 1,003,916
Outstanding, Weighted Average Exercise Price (in dollars per share) $ 5.17 $ 4.72 $ 4.18
Exercisable, Number of Shares (in shares) 541,238    
Exercisable, Weighted Average Exercise Price (in dollars per share) $ 4.61    
Exercisable, Weighted Average Fair Value (in dollars per share) $ 2.01    
Exercisable, Weighted Average Remaining Contractual Life (Year) 6 years 73 days