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Assumptions Used to Estimate Fair Value of Employee Stock Purchase Plan (Detail)
3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividend yield   0.00%
Expected volatility, Minimum   33.00%
Expected volatility, Maximum   49.00%
Risk-free interest rate, Minimum   0.20%
Risk-free interest rate, Maximum   1.60%
Expected forfeiture   10.00%
Contractual term of up to   7 years
Employee stock purchase plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividend yield 0.00% 0.00%
Expected volatility   36.00%
Expected volatility, Minimum 36.00%  
Expected volatility, Maximum 57.00%  
Risk-free interest rate   0.10%
Risk-free interest rate, Minimum 0.30%  
Risk-free interest rate, Maximum 0.50%  
Expected forfeiture 0.00% 0.00%
Contractual term of up to 24 months 24 months