Equity Incentive Plans - Schedule of Fair Value of Option Award and ESPP on Grant Date (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Stock options [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Risk-free interest rate | 1.50% | 1.60% | 1.90% |
| Expected term (in years) | 6 years 2 months 12 days | 5 years 4 months 24 days | 6 years |
| Expected volatility | 47.00% | 48.00% | 55.00% |
| Dividend yield | 0.00% | 0.00% | 0.00% |
| Employee stock purchase plan [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Risk-free interest rate | 0.60% | 0.30% | 0.10% |
| Expected term (in years) | 6 months | 6 months | 6 months |
| Expected volatility | 41.00% | 42.00% | 46.00% |
| Dividend yield | 0.00% | 0.00% | 0.00% |