Stockholders Equity (Deficit) - Schedule of Reserved Shares of Common Stock for Issuance (Details) - shares	Sep. 30, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	11,554,677	44,793,329
2018 Equity Incentive Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	0
2020 Stock Option and Grant Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	4,338,284
Unvested Restricted Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	3,554,488	4,403,148
Option To Purchase Common Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	3,661,905	44,960
Stock Available for Grant | 2018 Equity Incentive Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance		486,082
Stock Available for Grant | 2020 Stock Option and Grant Plan
Class Of Stock [Line Items]
Reserved shares of common stock for issuance	4,338,284
Preferred Stock
Class Of Stock [Line Items]
Reserved shares of common stock for issuance		39,859,139