Basis of Presentation and Summary of Significant Accounting Policies - Antidilutive Shares Excluded From Computation of Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	9,850,201	8,058,357
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	7,983,370	6,126,560
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	1,866,831	1,878,660
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	0	53,137