Annual report pursuant to Section 13 and 15(d)

Note 10 - Summary of Stock Options - Summary of Option Activity Under All Plans (Details)

v3.19.1
Note 10 - Summary of Stock Options - Summary of Option Activity Under All Plans (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Options outstanding, Shares (in shares) 2,694,224 1,909,764  
Options outstanding, Weighted average exercise price (in dollars per share) $ 5.80 $ 6.19  
Options outstanding, Weighted Average Remaining Contractual Term (Year) 7 years 146 days 8 years 219 days 9 years 36 days
Options outstanding, Aggregate Intrinsic Value   $ 249,154 $ 211,396
Options granted, Shares (in shares) 2,358,559 1,000,985  
Options granted, Weighted average exercise price (in dollars per share) $ 3.52 $ 5.68  
Options exercised, Shares (in shares) (7,730)  
Options exercised, Weighted average exercise price (in dollars per share) $ 4.02  
Options canceled, Shares (in shares) (1,038,308) (208,795)  
Options canceled, Weighted average exercise price (in dollars per share) $ 5.43 $ 8.88  
Options outstanding, Shares (in shares) 4,014,475 2,694,224 1,909,764
Options outstanding, Weighted average exercise price (in dollars per share) $ 4.56 $ 5.80 $ 6.19
Vested and exercisable and expected to vest, end of period, Number Of Shares (in shares) 3,825,887    
Vested and exercisable and expected to vest, end of period, Weighted Average Exercise Price (in dollars per share) $ 4.98    
Vested and exercisable and expected to vest, end of period, Weighted Average Remaining Contractual Term (Year) 7 years 109 days    
Vested and exercisable, end of period, Number Of Shares (in shares) 1,637,474    
Vested and exercisable, end of period, Weighted Average Exercise Price (in dollars per share) $ 5.44    
Vested and exercisable, end of period, Weighted Average Remaining Contractual Term (Year) 5 years