Net Loss Per Share - Summary of Antidilutive Securities Excluded From Computation Diluted Weighted Average Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	5,991,771	5,610,053	20,148,104
Unvested Restricted Stock [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	585,004	1,149,257	4,185
Unvested Restricted Stock Units [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	734,577
Warrants to Purchase Common Stock [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount		100,000	200,000
Employee Stock Purchase Plan [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	91,815	114,271
Redeemable Convertible Preferred Stock [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount			16,382,615
Options to Purchase Common Stock [Member]
Schedule Of Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	4,580,375	4,246,525	3,561,304