Significant Accounting Policies - Summary of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares, total	12,755,226	2,326,682	2,923,003
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares, total	2,695,796	1,374,359	1,803,574
Unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares, total	4,430	22,150	41,657
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares, total	0	3,333	150,932
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares, total	10,055,000	926,840	926,840