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Assumptions Used to Estimate Fair Value of Employee Stock Purchase Plan (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected dividend yield 0.00% 0.00% 0.00% 0.00%
Expected volatility, Minimum 40.00% 35.00% 40.00% 33.00%
Expected volatility, Maximum 49.00% 49.00% 49.00% 49.00%
Risk-free interest rate, Minimum 0.50% 0.30% 0.50% 0.20%
Risk-free interest rate, Maximum 1.50% 2.40% 1.50% 2.40%
Expected forfeiture   10.00%   10.00%
Contractual term of up to 10 years 10 years 10 years 10 years
Employee stock purchase plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected dividend yield 0.00% 0.00% 0.00% 0.00%
Expected volatility, Minimum 29.00% 35.00% 29.00% 35.00%
Expected volatility, Maximum 48.00% 36.00% 57.00% 36.00%
Risk-free interest rate, Minimum 0.40% 0.20% 0.30% 0.10%
Risk-free interest rate, Maximum 0.50% 0.30% 0.50% 0.30%
Expected forfeiture 0.00% 0.00% 0.00% 0.00%
Contractual term of up to 24 months 24 months 24 months 24 months