Stockholders' Equity (Deficit) - Convertible Preferred Stock Warrants - Additional Information (Details) - shares	Dec. 31, 2018	Dec. 31, 2017	Oct. 02, 2017	Oct. 01, 2017
Class Of Warrant Or Right [Line Items]
Preferred stock, shares outstanding	0	0
Class B Common Stock
Class Of Warrant Or Right [Line Items]
Outstanding warrants to purchase	0	200,000
Warrants exercised		1,900,000
Warrants cancelled		100,000
Warrants issued		1,800,000
Initial Public Offering | Class B Common Stock
Class Of Warrant Or Right [Line Items]
Outstanding warrants to purchase			2,200,000
Convertible Preferred Stock Warrants
Class Of Warrant Or Right [Line Items]
Preferred stock, shares outstanding				2,200,000