Fair Value Measurements - Assumptions (Detail) |
12 Months Ended | ||
|---|---|---|---|
Sep. 26, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Series Seed preferred stock warrants | |||
| Fair Value of preferred stock warrants | |||
| Expected term (years) | 4 years 10 months 24 days | 5 years 8 months 12 days | 6 years 8 months 12 days |
| Expected volatility | 59.10% | 60.30% | 53.90% |
| Risk-free interest rate | 1.12% | 1.84% | 1.97% |
| Estimated dividend yield | 0.00% | 0.00% | 0.00% |
| Series A-3 preferred stock warrants | |||
| Fair Value of preferred stock warrants | |||
| Expected term (years) | 6 years 6 months | 7 years 2 months 12 days | 8 years 2 months 12 days |
| Expected volatility | 59.10% | 61.30% | 54.10% |
| Risk-free interest rate | 1.34% | 2.09% | 2.07% |
| Estimated dividend yield | 0.00% | 0.00% | 0.00% |