Annual report pursuant to Section 13 and 15(d)

Share Based Compensation (Share Based Compensation Plans) (Details)

v3.8.0.1
Share Based Compensation (Share Based Compensation Plans) (Details) - shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock awards granted 153,100 137,258 135,150  
Restricted stock awards forfeited (2,444) (2,867) 0  
Restricted Stock Unit, Converted to shares and issued to Deferred Compensation Plan 0 0 217  
Stock Option, Outstanding as of December 31, 1,546,014 1,639,865 1,690,899 1,546,508
Total Options, Granted, Number of Shares 1,013,893 197,550 192,350  
Stock Options, Exercised, Number of Shares 562,587 113,820 40,461  
Stock Options, Forfeited, Number of Shares (3,374) (18,760) 0  
Stock Options, Expired, Number of Shares 541,783 116,004 7,498  
Stock Issued During Period, Shares, Employee Stock Purchase Plans 36,552 41,924 39,384  
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 896,265 522,341 764,567  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Period Increase (Decrease) 846,353      
Director [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Director stock awards granted 1,750 3,125 3,375