Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Convertible preferred stock, shares authorized	80,104,464	80,104,464
Convertible preferred stock, shares outstanding	78,267,369	78,267,369
Convertible preferred stock, shares issued	78,627,369	78,627,369
Convertible preferred stock, liquidation preference	$ 501,410,000	$ 501,410,000
Common stock, par value (in usd per share)	$ 0.0000001	$ 0.0000001
Common stock, shares authorized	111,853,396	111,853,396
Common stock, shares outstanding	13,002,822	11,896,882
Common stock, shares issued	13,002,822	11,896,882
Convertible Preferred Stock
Convertible preferred stock, par value (in usd per share)	$ 0.0000001	$ 0.0000001
Convertible preferred stock, shares authorized	80,104,464	80,104,464
Convertible preferred stock, shares outstanding	78,627,369	78,627,369
Convertible preferred stock, shares issued	78,627,369	78,627,369
Convertible preferred stock, liquidation preference		$ 501,410