Stock-Based Compensation - Summary of Assumptions Used in Black-Scholes Option Pricing Model (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Risk-free interest rate, minimum | 1.19% | 1.43% | 1.64% |
| Risk-free interest rate, maximum | 1.93% | 1.89% | 2.72% |
| Expected volatility, minimum | 67.80% | 64.00% | 64.90% |
| Expected volatility, maximum | 77.80% | 67.40% | 71.30% |
| Expected dividend yield | 0.00% | 0.00% | 0.00% |
| Employee and Board of Directors Options [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected life of options (in years) | 6 years 3 months | 6 years 3 months | 6 years 3 months |
| Nonemployee Options [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected life of options (in years) | 10 years | 10 years | 10 years |