Annual report pursuant to Section 13 and 15(d)

Share Based Compensation (Schedule of Share-based Compensation, Stock Options, Activity) (Details)

v3.20.4
Share Based Compensation (Schedule of Share-based Compensation, Stock Options, Activity) (Details) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Stock Option Activities:      
Outstanding as of the beginning of year (in shares) 1,454,074 1,467,391 1,546,014
Granted (in shares) 175,800 165,650 142,550
Exercised (in shares) (123,829) (165,893) (220,694)
Expired (in shares) (5,986) (7,874) (479)
Outstanding as of the end of year (in shares) 1,500,059 1,454,074 1,467,391
Outstanding and Exercisable, end of period (in shares) 1,070,779    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]      
Outstanding, beginning balance, Weighted Average Exercise Price (in dollars per share) $ 43.19    
Granted, Weighted Average Exercise Price (in dollars per share) 31.88    
Exercised, Weighted Average Exercise Price (in dollars per share) 35.79    
Expired, Weighted Average Exercise Price (in dollars per share) 49.71    
Outstanding, ending balance, Weighted Average Exercise Price (in dollars per share) 42.45 $ 43.19  
Outstanding and Exercisable, end of period, Weighted Average Exercise Price (in dollars per share) $ 44.08