Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total common stock reserved for future issuance	4,224,363	3,218,710
Stock Options Issued and Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total common stock reserved for future issuance	2,474,461	1,821,093
Warrants for Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total common stock reserved for future issuance	80,428	80,428
Awards Available Under 2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total common stock reserved for future issuance	1,031,387	813,473
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total common stock reserved for future issuance	638,087	503,716