Quarterly report pursuant to Section 13 or 15(d)

Note 6 - Employee and Director Benefits - Summary of Stock Option Activity (Details)

v3.10.0.1
Note 6 - Employee and Director Benefits - Summary of Stock Option Activity (Details) - Employee Stock Option [Member] - USD ($)
$ / shares in Units, $ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Outstanding, shares (in shares) 1,666,834 2,026,334 2,026,334  
Outstanding, weighted average exercise price (in dollars per share) $ 10.68 $ 9 $ 9  
Outstanding, weighted average remaining contractual term (Year) 5 years 36 days 5 years 255 days 5 years 182 days 6 years 73 days
Outstanding, aggregate intrinsic value $ 38,998 $ 45,136 $ 51,377 $ 57,636
Granted (in shares) 12,750 52,500    
Granted, weighted average exercise price (in dollars per share) $ 41.58 $ 37.93    
Granted, weighted average remaining contractual term (Year) 9 years 182 days 9 years 146 days    
Granted, aggregate intrinsic value $ (31) $ (35)    
Exercised (in shares) (231,336) (359,000)    
Exercised, weighted average exercise price (in dollars per share) $ 4.94 $ 4.97    
Exercised, weighted average remaining contractual term (Year) 3 years 36 days 4 years 73 days    
Exercised, aggregate intrinsic value $ 7,665 $ 11,590    
Forfeited (in shares) (33,000) (32,000)    
Forfeited, weighted average exercise price (in dollars per share) $ 15 $ 21.96    
Forfeited, weighted average remaining contractual term (Year) 6 years 146 days 8 years 146 days    
Forfeited, aggregate intrinsic value $ 758 $ 489    
Outstanding, shares (in shares) 1,415,248 1,687,834 1,666,834 2,026,334
Outstanding, weighted average exercise price (in dollars per share) $ 11.79 $ 10.51 $ 10.68 $ 9
Exercisable, shares (in shares) 693,100 810,736    
Exercisable, weighted average exercise price (in dollars per share) $ 6.78 $ 5.22    
Exercisable, weighted average remaining contractual term (Year) 3 years 182 days 4 years 73 days    
Exercisable, aggregate intrinsic value $ 22,513 $ 25,971