Stockholders' Equity (Deficit) - Shares Reserved for Future Issuance (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	6,237,832	28,499,408
Warrants to purchase common stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	0	7,527
Exercise of options under stock plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	4,310,790	4,364,377
Issuance of options under stock plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	1,554,690	57,889
Issuance of common stock under employee stock purchase plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	372,352	0
Conversion of Series A redeemable convertible preferred stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	0	1,629,629
Conversion of Series A-1 redeemable convertible preferred stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	0	1,111,111
Conversion of Series B redeemable convertible preferred stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	0	6,264,470
Conversion of Series C redeemable convertible preferred stock and warrants
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	0	15,064,405