Stock Option Plans - Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted to Employees and Non Employees (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Expected life | 6 years | 6 years | 6 years |
| Risk-free interest rate, minimum | 1.45% | 1.71% | 1.09% |
| Risk-free interest rate, maximum | 2.02% | 2.00% | 1.92% |
| Expected volatility, minimum | 51.00% | 54.00% | 59.00% |
| Expected volatility, maximum | 63.00% | 60.00% | 79.00% |
| Non Employee Awards [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Expected life | 10 years | 8 years | 7 years |
| Risk-free interest rate, minimum | 2.10% | 1.86% | 1.11% |
| Risk-free interest rate, maximum | 2.25% | 2.53% | 2.86% |
| Expected volatility, minimum | 60.00% | 56.00% | 56.00% |
| Expected volatility, maximum | 61.00% | 62.00% | 79.00% |