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Stock-Based Compensation - Status of Nonvested Restricted Stock, Stock Grants, Stock Units and Performance Shares (Details) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Restricted Stock Units, Stock Grants, and Stock Units      
Nonvested shares      
Balance at the beginning of the period (in shares) 270,991    
Granted (in shares) 109,106    
Vested (in shares) (132,102)    
Forfeited (in shares) (5,383)    
Balance at the end of the period (in shares) 242,612 270,991  
Weighted-Average Grant-Date Fair Value      
Balance at the beginning of the period (in dollars per share) $ 74.39    
Granted (in dollars per share) 89.15 $ 77.51 $ 72.60
Vested (in dollars per share) 73.48    
Forfeited (in dollars per share) 80.10    
Balance at the end of the period (in dollars per share) $ 81.38 $ 74.39  
Vested Awards Outstanding at December 31, 2017 (in shares) 67,148    
Vested Awards Outstanding at December 31, 2017 (in dollars per share)    
Number of nonvested awards to be settled in cash (in shares) 141,621    
Performance Shares      
Nonvested shares      
Balance at the beginning of the period (in shares) 312,384    
Granted (in shares) 142,874    
Vested (in shares) (139,214)    
Forfeited (in shares) (9,074)    
Balance at the end of the period (in shares) 306,970 312,384  
Weighted-Average Grant-Date Fair Value      
Balance at the beginning of the period (in dollars per share) $ 77.67    
Granted (in dollars per share) 92.16 $ 76.56 $ 78.99
Vested (in dollars per share) 78.99    
Forfeited (in dollars per share) 81.03    
Balance at the end of the period (in dollars per share) $ 83.65 $ 77.67  
Vested Awards Outstanding at December 31, 2017 (in shares) 139,214    
Vested Awards Outstanding at December 31, 2017 (in dollars per share)