Significant Accounting Policies - Schedule of Computation of Diluted EPS (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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)	9,226,277	7,662,325	12,102,215
2014 Convertible Notes
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)	0	0	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)	8,425,551	6,935,119	6,457,343
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)	4,500	154,500	157,500
Nonvested restricted 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)	754,415	572,706	447,049
Nonvested restricted stock units
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)	41,811	0	0