Stockholders' Equity - Stock Reserved for Future Issuance (Details)	Dec. 31, 2019 shares
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	17,758,849
Warrants to purchase common stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	9,692,879
Stock Option Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	7,923,098
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	142,872