Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details)

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Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details) - shares
Dec. 31, 2019
Dec. 31, 2018
Temporary Equity [Line Items]    
Reserved common stock 7,357,234 6,250,381
Common Stock    
Temporary Equity [Line Items]    
Reserved common stock 3,872,664 3,111,718
Common Stock Awards Issued And Outstanding    
Temporary Equity [Line Items]    
Reserved common stock 335,799 311,240
2004 and 2018 Equity Incentive Plan    
Temporary Equity [Line Items]    
Reserved common stock 2,750,416 2,525,610
2018 Employee Stock Purchase Plan    
Temporary Equity [Line Items]    
Reserved common stock 326,542 230,000
Warrants to Purchase Common Stock    
Temporary Equity [Line Items]    
Reserved common stock 71,813 71,813