Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Earnings Per Share [Abstract] | |||
| Net loss | $ (49,857) | $ (32,627) | $ (18,873) |
| Accretion of preferred stock to redemption value | (35,061) | (52,336) | (33,553) |
| Beneficial conversion charge relating to IPO participation payment | (14,161) | ||
| Net loss attributable to common stockholders, basic and diluted | $ (99,079) | $ (84,963) | $ (52,426) |
| Weighted-average common shares outstanding, basic and diluted | 24,740,480 | 12,770,916 | 12,549,266 |
| Net loss per share attributable to common stockholders, basic and diluted | $ (4.00) | $ (6.65) | $ (4.18) |