Significant Accounting Policies - Schedule of Computation of Diluted EPS (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Convertible notes payable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the computation of diluted net loss (in shares)	5,040,323	5,040,323	5,040,323
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the computation of diluted net loss (in shares)	5,255,930	4,583,586	3,826,459
Stock purchase warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the computation of diluted net loss (in shares)	157,500	157,500	309,506
Unvested restricted common stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the computation of diluted net loss (in shares)	164,194	119,993	103,064
2014 Notes | Convertible debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Ownership cap for holder and affiliates (in percentage)	9.985%