Quarterly report pursuant to Section 13 or 15(d)

Share-Based Payments - Stock Option Activity (Details)

v3.5.0.2
Share-Based Payments - Stock Option Activity (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense $ 2,093 $ 1,886 $ 6,204 $ 5,562
Employee Stock Option [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense 377 352 1,101 1,029
Tax benefit related to share-based expense 140 137 407 403
Unrecognized share-based compensation, net of estimated forfeitures $ 2,036 $ 1,977 $ 2,036 $ 1,977
Weighted average period over which unrecognized compensation will be recognized (years) 1 year 10 months 11 days   1 year 10 months 11 days  
Employee activity - stock options [Abstract]        
Stock option grants expire (in years)     7 years  
Grants, vesting period (in years)     3 years  
Expected dividend yield (in hundredths)   1.20% 1.00% 1.00%
Expected stock price volatility   29.80% 29.00% 33.70%
Weighted Average Risk Free Interest Rate   1.40% 1.30% 1.60%
Expected life of options (in years)   4 years 6 months 11 days 6 years 11 days 6 years 11 days
Weighted-average fair value of options (dollars per share)   $ 12 $ 12 $ 16
Outstanding, beginning of period (in shares) 855   786  
Granted (in shares)     122  
Exercised (in shares) (263)   (311)  
Forfeited (in shares)     (5)  
Outstanding, end of period (in shares) 592   592  
Exercisable, end of period (in shares) 364   364  
Outstanding, beginning of period (in dollars per share) $ 34   $ 32  
Grants in Period (in dollars per share)     44  
Exercises in Period (in dollars per share) 23   23  
Forfeited in period (in dollars per share)     38  
Outstanding, end of period (in dollars per share) 40   40  
Exercisable, end of period (in dollars per share) $ 36   $ 36  
Aggregate Intrinsic Value Outstanding, end of period $ 3,355   $ 3,355  
Aggregate Intrinsic Value Exercisable, end of period $ 3,351   $ 3,351  
Weighted-average remaining contractual term Outstanding, end of period (in years) 4 years 11 days   4 years 11 days  
Weighted-average remaining contractual term Exercisable, end of period (in years) 2 years 9 months 11 days   2 years 9 months 11 days