XML 130 R95.htm IDEA: XBRL DOCUMENT v3.20.4
Stock-Based Compensation - Summary Information for Restricted Stock Awards and Incentive Compensation Stock Awards (Detail) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Restricted Stock - Service Based Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of Awards, January 1, 2020 183,939    
Number of Awards, Awarded 92,472    
Number of Awards, Distributed (66,797)    
Number of Awards, Forfeited (2,633)    
Number of Awards, December 31, 2020 206,981 183,939  
Weighted-Average Grant-Date Fair Value, January 1, 2020 $ 185.06    
Weighted-Average Grant-Date Fair Value, Awarded 222.39 $ 196.91 $ 211.03
Weighted-Average Grant-Date Fair Value, Distributed 194.94    
Weighted-Average Grant-Date Fair Value, Forfeited 206.08    
Weighted-Average Grant-Date Fair Value, December 31, 2020 $ 198.28 $ 185.06  
Restricted Stock - Performance Based Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of Awards, January 1, 2020 124,221    
Number of Awards, Awarded 38,272    
Number of Awards, Distributed (79,192)    
Number of Awards, Forfeited (1,367)    
Number of Awards, Adjustment for performance 36,642    
Number of Awards, December 31, 2020 118,576 124,221  
Weighted-Average Grant-Date Fair Value, January 1, 2020 $ 204.21    
Weighted-Average Grant-Date Fair Value, Awarded 266.97 $ 192.27 212.12
Weighted-Average Grant-Date Fair Value, Distributed 211.29    
Weighted-Average Grant-Date Fair Value, Forfeited 216.39    
Weighted-Average Grant-Date Fair Value, Adjustment for performance 211.29    
Weighted-Average Grant-Date Fair Value, December 31, 2020 $ 228.15 $ 204.21  
Incentive Compensation Stock Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of Awards, January 1, 2020 39,584    
Number of Awards, Awarded 21,082    
Number of Awards, Distributed (17,354)    
Number of Awards, Forfeited (689)    
Number of Awards, December 31, 2020 42,623 39,584  
Weighted-Average Grant-Date Fair Value, January 1, 2020 $ 198.83    
Weighted-Average Grant-Date Fair Value, Awarded 258.67 $ 192.27 $ 212.12
Weighted-Average Grant-Date Fair Value, Distributed 209.99    
Weighted-Average Grant-Date Fair Value, Forfeited 201.43    
Weighted-Average Grant-Date Fair Value, December 31, 2020 $ 223.85 $ 198.83