Net Loss per Share Attributable to Common Stockholders - Common Shares Excluded from the Calculation of Net Loss per Common Share Attributable to Common Stockholders (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	28,893,376	19,305,848
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	3,323,761	3,000,264
Common Stock Underlying Series A and Series A-1 Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share		16,300,969
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	25,569,615	4,615