Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock initially reserved for future issuance (shares)	5,714,588	4,199,733
Convertible preferred stock
Class of Stock [Line Items]
Common stock initially reserved for future issuance (shares)	0	2,850,276
Stock options issued and outstanding
Class of Stock [Line Items]
Common stock initially reserved for future issuance (shares)	1,282,847	436,341
Authorized for future stock awards, option grants, or employee stock purchase program
Class of Stock [Line Items]
Common stock initially reserved for future issuance (shares)	369,234	57,904
Preferred warrants
Class of Stock [Line Items]
Common stock initially reserved for future issuance (shares)	0	855,212
Common warrants
Class of Stock [Line Items]
Common stock initially reserved for future issuance (shares)	4,062,507	0