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Share-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation 14,020 10,319
Payment, Tax Withholding, Share-based Payment Arrangement $ 1,478 $ 977
Unrecognized compensation cost $ 7,300  
Awards to non-employee directors [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 84.47  
Granted awards (shares) 887  
Unrecognized compensation expense related to the awards to non-employee directors $ 100  
Total [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted awards (shares) 8,870  
Award to key employees [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expired In Period (852)  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 102.73  
Granted awards (shares) 66,425  
Vesting period 3 years  
Payment, Tax Withholding, Share-based Payment Arrangement $ 1,500  
Intrinsic value of the SICP awards $ 22,500  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (5,384)  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value $ 93.39  
Accelerated Vested Shares [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation 14,020