Stock-Based Compensation - Schedule of Assumptions Used to Determine Fair Value of Option Grants (Detail) |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2015 |
Jun. 30, 2014 |
Jun. 30, 2015 |
Jun. 30, 2014 |
|
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Risk-free interest rate, Minimum | 1.55% | 1.60% | 1.47% | 1.60% |
Risk-free interest rate, Maximum | 1.83% | 1.95% | 1.83% | 2.73% |
Expected volatility, Minimum | 85.63% | 97.91% | 85.63% | 97.91% |
Expected volatility, Maximum | 87.91% | 101.64% | 91.16% | 107.01% |
Weighted average expected volatility | 86.85% | 100.77% | 87.62% | 101.19% |
Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |
Minimum [Member] | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected lives (in years) | 5 years 2 months 12 days | 5 years 2 months 12 days | 5 years 2 months 12 days | 5 years 2 months 12 days |
Maximum [Member] | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected lives (in years) | 6 years 3 months | 6 years 3 months | 6 years 3 months | 10 years |