Preferred Stock Warrants - Additional Information (Details) - $ / shares	Oct. 22, 2018	Aug. 31, 2018	Dec. 31, 2017
Redeemable Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Common stock, warrants			486,356
2018 Series C-1 Warrants | Redeemable Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares		368,582
Exercise price of warrant		$ 0.12
2014 Series B, Convertible Debt Series C-1, and 2018 Series C-1 Warrants | Redeemable Convertible Preferred Stock and Common Stock | Initial Public Offering
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares	764,034
2014 Series B, Convertible Debt Series C-1, and 2018 Series C-1 Warrants | Redeemable Convertible Preferred Stock and Common Stock | Weighted-average | Initial Public Offering
Class Of Warrant Or Right [Line Items]
Exercise price of warrant	$ 0.12
Two Thousand Nine Series B And Term Loan Series C-1 Warrants | Initial Public Offering | Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Common stock, warrants	75,597