Note 3 - Net Income Per Common Share (Tables)
 9 Months Ended
Sep. 30, 2016
Notes Tables  
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
   
Three Months Ended
    
Nine Months Ended
  
   
September 30,
    
September 30,
  
(in thousands, except share and per share amounts)
  
2016
    
2015
    
2016
    
2015
  
Net income
   $ 11,982     $ 12,382     $ 33,335     $ 34,521  
                                 
Basic - weighted-average shares outstanding:
     26,416,041       26,083,405       26,334,738       25,952,451  
Effect of dilutive securities:
                                
Employee stock options and other
     193,837       297,908       204,340       338,307  
Diluted - weighted-average shares outstanding:
     26,609,878       26,381,313       26,539,078       26,290,758  
Net income per share:
                                
Basic
   $ 0.45     $ 0.47     $ 1.27     $ 1.33  
Diluted
   $ 0.45     $ 0.47     $ 1.26     $ 1.31