Stock-based Compensation - Schedule of Assumptions Used to Determine Fair Value of Option Grants (Detail) |
3 Months Ended | 6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Jun. 30, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Risk-free interest rate, Minimum | 1.55% | 1.18% | 1.47% | 1.47% | 1.60% |
| Risk-free interest rate, Maximum | 1.83% | 2.02% | 1.83% | 2.43% | 2.73% |
| Expected volatility, Minimum | 85.63% | 79.42% | 85.63% | 84.93% | 97.91% |
| Expected volatility, Maximum | 87.91% | 116.70% | 91.16% | 116.81% | 107.01% |
| Weighted average expected volatility | 86.85% | 88.64% | 87.62% | 89.26% | 101.52% |
| Expected dividend yield | 0.00% | 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 | 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 | 10 years | 6 years 3 months | 10 years | 10 years |