Net Loss Per Share Attributable to Common Stockholders - Summary of Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Earnings Per Share [Abstract] | |||||||||||
| Net loss | $ (15,635) | $ (16,944) | $ (16,176) | $ (14,084) | $ (14,587) | $ (11,193) | $ (11,355) | $ (10,804) | $ (62,839) | $ (47,939) | $ (18,518) |
| Accretion of preferred stock issuance costs to redemption value | (204) | (121) | |||||||||
| Accrued dividends on preferred stock | (2,267) | ||||||||||
| Net loss attributable to common stockholders-basic and diluted | $ (62,839) | $ (48,143) | $ (20,906) | ||||||||
| Weighted-average number of common shares-basic and diluted | 20,320,628 | 16,070,054 | 29,463 | ||||||||
| Net loss per share attributable to common stockholders-basic and diluted | $ (0.76) | $ (0.82) | $ (0.86) | $ (0.79) | $ (0.82) | $ (0.63) | $ (0.64) | $ (1.02) | $ (3.09) | $ (3.00) | $ (709.57) |