Basis of Presentation and Summary of Significant Accounting Policies - Antidilutive Shares Excluded From Computation of Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	10,473,986	8,023,711
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	7,748,519	6,138,373
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of net loss per common share	2,677,188	1,866,831
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	48,279	18,507