Quarterly report pursuant to Section 13 or 15(d)

Net Loss Per Share - Summary of Antidilutive Securities Excluded from Computation of Weighted Average Common Stock Outstanding (Detail)

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Net Loss Per Share - Summary of Antidilutive Securities Excluded from Computation of Weighted Average Common Stock Outstanding (Detail) - shares
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Series A Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 0 6,149 0 6,149
Series B Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 0 131,685 0 131,685
Series C Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 0 783,515 0 783,515
Series C-2 Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 0 173,213 0 173,213
Series D-1 Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 0 296,773 0 296,773
Series D-2 Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 0 300,549 0 300,549
Series C-1 Preferred warrants [Member] | Series C-1 Preferred [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 14,033 14,033 14,033 14,033
Stock options [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 1,153,369 215,467 1,153,369 215,467
ESPP [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities 7,298 0 7,298 0