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Share-Based Awards - Fair Value of Options Granted, Estimated at Date of Grant Using Black Scholes Merton Option Pricing Model (Detail) - Option awards - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected volatility 56.00% 51.00%    
Expected dividend yield 0.00% 0.00% 0.00% 0.00%
Risk-free interest rate 0.74% 0.33%    
Weighted-average expected life 4 years 6 months 5 years    
Weighted-average fair value of options granted (usd per share) $ 53.16 $ 20.21 $ 59.58 $ 20.69
Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected volatility     52.00% 45.00%
Risk-free interest rate     0.57% 0.33%
Weighted-average expected life     4 years 6 months 5 years
Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected volatility     56.00% 51.00%
Risk-free interest rate     0.90% 0.93%
Weighted-average expected life     5 years 9 months 5 years 6 months