Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Common Share (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Earnings Per Share [Abstract]        
Net loss $ (8,444) $ (5,919) $ (16,766) $ (12,208)
Accretion of preferred stock issuance costs to redemption value   (117)   (234)
Accrued dividends on redeemable convertible preferred stock   (1,295)   (2,515)
Net loss attributable to common stockholders $ (8,444) $ (7,331) $ (16,766) $ (14,957)
Weighted-average number of common shares-basic and diluted 16,464,410 2,210,766 16,444,210 2,190,479
Net loss per share attributable to common stockholders-basic and diluted $ (0.51) $ (3.32) $ (1.02) $ (6.83)