Shareholders' Deficit - Summary of Reserved Shares of Common Stock (Details)	Jun. 30, 2019 shares
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	114,004,082
Exercise of Outstanding Common Stock Options
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	17,681,436
Stock Option Grants
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	3,155,968
Conversion of Common Stock Warrants
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	55,032
Conversion of All Series of Convertible Preferred Stock
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	93,039,737
Series E-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	15,034
Conversion of Series C Convertible Preferred Stock in Connection with Warrant Exercise
Class Of Stock [Line Items]
Shares of common stock reserved for future issuance	56,875