Preferred Stock, Common Stock and Stockholders' Equity - Summary of Estimated Fair Value of Employee Stock Purchase Plan Award (Detail) - Employee stock purchase plan [Member] |
12 Months Ended | |
|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Stock-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Expected option term | 6 months | 6 months |
| Expected dividend yield | 0.00% | 0.00% |
| Minimum [Member] | ||
| Stock-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Risk free interest rate | 0.08% | 0.05% |
| Expected volatility of common stock | 62.91% | 69.32% |
| Maximum [Member] | ||
| Stock-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Risk free interest rate | 0.26% | 0.08% |
| Expected volatility of common stock | 69.64% | 73.21% |