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Share-Based Compensation - Summary of Restricted Stock Activity (Detail) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Weighted Average Grant Price      
Granted $ 98.09 $ 96.38 $ 106.43
Restricted Stock      
Shares Outstanding      
Beginning Balance 1,386,009    
Granted 391,206    
Vested (423,154)    
Canceled/Forfeited (210,985)    
Ending Balance 1,143,076 1,386,009  
Expected to vest as of end of period 1,135,950    
Weighted Average Grant Price      
Beginning Balance $ 96.92    
Granted 92.23 $ 89.75 $ 114.42
Vested 87.93    
Canceled/Forfeited 99.28    
Ending Balance 98.20 $ 96.92  
Expected to vest as of end of period $ 98.12