Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
Note 6 - Employee and Director Benefits - Summary of Stock Option Activity (Details) - Employee Stock Option [Member] - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Mar. 31, 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 182 days 6 years 73 days 5 years 182 days 6 years 73 days
Outstanding, aggregate intrinsic value $ 43,978 $ 49,540 $ 51,377 $ 57,636
Granted (in shares) 10,250 51,500    
Granted, weighted average exercise price (in dollars per share) $ 41.21 $ 38.10    
Granted, weighted average remaining contractual term (Year) 9 years 328 days 9 years 292 days    
Granted, aggregate intrinsic value $ (4) $ (89)    
Exercised (in shares) (173,836) (175,500)    
Exercised, weighted average exercise price (in dollars per share) $ 4.90 $ 5.28    
Exercised, weighted average remaining contractual term (Year) 3 years 146 days 5 years    
Exercised, aggregate intrinsic value $ 6,244 $ 5,459    
Forfeited (in shares) (1,000) (27,000)    
Forfeited, weighted average exercise price (in dollars per share) $ 25.41 $ 21.55    
Forfeited, weighted average remaining contractual term (Year) 8 years 182 days 8 years 292 days    
Forfeited, aggregate intrinsic value $ 15 $ 401    
Outstanding, shares (in shares) 1,502,248 1,875,334 1,666,834 2,026,334
Outstanding, weighted average exercise price (in dollars per share) $ 11.54 $ 9.96 $ 10.68 $ 9
Exercisable, shares (in shares) 672,600 928,236    
Exercisable, weighted average exercise price (in dollars per share) $ 5.48 $ 5.12    
Exercisable, weighted average remaining contractual term (Year) 3 years 328 days 4 years 219 days    
Exercisable, aggregate intrinsic value $ 23,770 $ 29,013