Convertible Preferred Stock and Stockholders' Equity - Summary of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (Details) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Common stock, par value	$ 0.0001	$ 0.0001
Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, par value		$ 0.0001