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Stock-based Compensation (Detail)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield (in percent) 0.00%    
ESPP obligations      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility, minimum 30.00% 30.00% 26.00%
Expected volatility, maximum 60.00% 49.00% 31.00%
Expected term (in years) 6 months 6 months 6 months
Risk-free interest rate. minimum 0.11% 2.04% 1.15%
Risk-free interest rate, maximum 2.04% 2.46% 2.22%
Dividend yield (in percent) 0.00% 0.00% 0.00%