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Stock-Based Compensation Plans (Details)
$ / shares in Units, $ in Thousands
9 Months Ended
Sep. 30, 2020
USD ($)
Type
$ / shares
shares
Sep. 30, 2019
USD ($)
Restricted and Performance Stock Grants [Abstract]    
Number of types of restricted stock | Type 2  
Additional Disclosures [Abstract]    
Compensation expense, gross | $ $ 6,067 $ 5,742
Restricted Shares [Member] | Minimum [Member]    
Restricted and Performance Stock Grants [Abstract]    
Expiration of vesting period 3 years  
Restricted Shares [Member] | Employees [Member]    
Restricted and Performance Stock Grants [Abstract]    
Estimated forfeitures 5.00%  
Restricted Shares [Member] | Executives [Member]    
Restricted and Performance Stock Grants [Abstract]    
Estimated forfeitures 0.00%  
Restricted Shares [Member] | Directors [Member]    
Restricted and Performance Stock Grants [Abstract]    
Estimated forfeitures 0.00%  
Restricted Shares [Member] | Age 60 [Member] | Executives [Member]    
Restricted and Performance Stock Grants [Abstract]    
Vesting percentage 25.00%  
Vesting period before reaching age limit 2 months  
Restricted Shares [Member] | Age 63 [Member] | Executives [Member]    
Restricted and Performance Stock Grants [Abstract]    
Vesting percentage 25.00%  
Vesting period before reaching age limit 2 months  
Restricted Shares [Member] | Age 65 [Member] | Executives [Member]    
Restricted and Performance Stock Grants [Abstract]    
Vesting percentage 100.00%  
Vesting period before reaching age limit 2 months  
Performance-based Shares [Member]    
Restricted and Performance Stock Grants [Abstract]    
Measuring period for performance-based shares 3 years  
Performance-based Shares [Member] | Minimum [Member]    
Restricted and Performance Stock Grants [Abstract]    
Expiration of vesting period 3 years  
Restricted and Performance-Based Shares [Member]    
Restricted and performance-based stock, shares [Roll Forward]    
Beginning of period (in shares) | shares 852,540  
Granted (in shares) | shares 208,525  
Vested (in shares) | shares (67,404)  
Forfeited (in shares) | shares (6,750)  
End of period (in shares) | shares 986,911  
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward]    
Beginning of period (in dollars per share) | $ / shares $ 35.26  
Granted (in dollars per share) | $ / shares 38.22  
Vested (in dollars per share) | $ / shares 33.53  
Forfeited (in dollars per share) | $ / shares 43.74  
End of period (in dollars per share) | $ / shares $ 35.98  
Additional Disclosures [Abstract]    
Compensation expense, gross | $ $ 5,700 5,300
Compensation expense, net of tax | $ 4,300 $ 3,900
Unamortized compensation expense | $ $ 17,500  
Restricted and Performance-Based Shares [Member] | Employees [Member]    
Additional Disclosures [Abstract]    
Weighted average period of recognition for unrecognized compensation expense 4 years 1 month 6 days  
Restricted and Performance-Based Shares [Member] | Directors [Member]    
Additional Disclosures [Abstract]    
Weighted average period of recognition for unrecognized compensation expense 9 months 18 days  
Restricted and Performance-Based Shares [Member] | Executives and Directors [Member] | Minimum [Member]    
Restricted and Performance Stock Grants [Abstract]    
Post vesting holding period for restricted and performance shares issued 1 year  
Restricted and Performance-Based Shares [Member] | Executives and Directors [Member] | Maximum [Member]    
Restricted and Performance Stock Grants [Abstract]    
Post vesting holding period for restricted and performance shares issued 2 years