Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity, Stock Options and Net Income per Share - Stock Option Activity (Details)

v3.19.3.a.u2
Shareholders' Equity, Stock Options and Net Income per Share - Stock Option Activity (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation $ 11,907 $ 10,549 $ 8,103
Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate   1.10% 1.30%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate   24.40% 28.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate   2.70% 2.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term 7 years 6 years 1 month 6 days 5 years 10 months 24 days
Outstanding at beginning of year (shares) 538 440 564
Granted (shares)   193 128
Exercise of stock options (in shares) (99) (95) (206)
Forfeited (shares) (8)   (46)
Outstanding at end of year (shares) 431 538 440
Exercisable at end of year 272 230 226
Weighted Average Outstanding at beginning of year (per share) $ 51 $ 45 $ 41
Weighted average exercise price for options granted in the period   62 48
Weighted average exercise price for options exercised in the period 43 41 35
Weighted average exercise price for options forfeited in the period 54   46
Weighted Average Outstanding at end of year (per share) 53 51 45
Weighted average exercise price for options exercisable at year end $ 50 45 42
Weighted-average fair value of options granted during the year (dollars per share)   $ 16 $ 13
Aggregate intrinsic value of options exercised $ 2,388 $ 1,992 $ 3,569
Average aggregate intrinsic value for options outstanding 4,147    
Average aggregate instrinsic value for exercisable options 3,497    
Share-based compensation 1,597 1,578 1,313
Tax benefit related to share-based compensation expense 403 $ 398 $ 466
Unrecognized compensation cost $ 1,490    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition 1 year 4 months 24 days    
Exercise Price Range 42.48 through 44.90 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 93    
Exercisable at end of year 93    
Weighted Average Outstanding at end of year (per share) $ 43.63    
Weighted average exercise price for options exercisable at year end 43.63    
Range of exercise price, lower range limit 42.48    
Range of exercise price, upper range limit $ 44.90    
Weighted average remaining contractual life 2 years 9 months 18 days    
Exercise Price Range 45.34 through 48.32 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 100    
Exercisable at end of year 69    
Weighted Average Outstanding at end of year (per share) $ 47.73    
Weighted average exercise price for options exercisable at year end 47.69    
Range of exercise price, lower range limit 45.34    
Range of exercise price, upper range limit $ 48.32    
Weighted average remaining contractual life 4 years    
Exercise Price Range 50.71 through 53.73 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 49    
Exercisable at end of year 47    
Weighted Average Outstanding at end of year (per share) $ 51.16    
Weighted average exercise price for options exercisable at year end 51.07    
Range of exercise price, lower range limit 50.71    
Range of exercise price, upper range limit $ 53.73    
Weighted average remaining contractual life 2 years 4 months 24 days    
Exercise Price Range 57.18 through 60.42 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 88    
Exercisable at end of year 29    
Weighted Average Outstanding at end of year (per share) $ 58.80    
Weighted average exercise price for options exercisable at year end 58.68    
Range of exercise price, lower range limit 57.18    
Range of exercise price, upper range limit $ 60.42    
Weighted average remaining contractual life 5 years 1 month 6 days    
Exercise Price Range 64.26 through 64.26 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 100    
Exercisable at end of year 33    
Weighted Average Outstanding at end of year (per share) $ 64.26    
Weighted average exercise price for options exercisable at year end 64.26    
Range of exercise price, lower range limit 64.26    
Range of exercise price, upper range limit $ 64.26    
Weighted average remaining contractual life 5 years 8 months 12 days    
Exercise Price Range 42.48 through 64.26 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 430    
Exercisable at end of year 271    
Weighted Average Outstanding at end of year (per share) $ 53.33    
Weighted average exercise price for options exercisable at year end 50.08    
Range of exercise price, lower range limit 42.48    
Range of exercise price, upper range limit $ 64.26    
Weighted average remaining contractual life 4 years 2 months 12 days