Redeemable Convertible Preferred Stock - Schedule Of Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	76,141,345	76,141,345
Redeemable convertible preferred stock, shares issued	61,279,079	61,279,079
Redeemable convertible preferred stock, shares outstanding	61,279,079	61,279,079
Net Carrying Value	$ 166,486	$ 166,486
Redeemable convertible preferred stock, liquidation preference	$ 120,047	$ 120,047
Series A-1 Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	10,141,345	10,141,345
Redeemable convertible preferred stock, shares issued	9,142,770	9,142,770
Redeemable convertible preferred stock, shares outstanding	9,142,770	9,142,770
Net Carrying Value	$ 72,181	$ 72,181
Redeemable convertible preferred stock, liquidation preference	$ 91,427	$ 91,427
Series A-2 Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	60,000,000	60,000,000
Redeemable convertible preferred stock, shares issued	47,124,931	47,124,931
Redeemable convertible preferred stock, shares outstanding	47,124,931	47,124,931
Net Carrying Value	$ 65,853	$ 65,853
Redeemable convertible preferred stock, liquidation preference	$ 5	$ 5
Series B-1 Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	5,854,982	5,854,982
Redeemable convertible preferred stock, shares issued	4,866,360	4,866,360
Redeemable convertible preferred stock, shares outstanding	4,866,360	4,866,360
Net Carrying Value	$ 27,628	$ 27,628
Redeemable convertible preferred stock, liquidation preference	$ 27,787	$ 27,787
Series B-2 Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	145,018	145,018
Redeemable convertible preferred stock, shares issued	145,018	145,018
Redeemable convertible preferred stock, shares outstanding	145,018	145,018
Net Carrying Value	$ 824	$ 824
Redeemable convertible preferred stock, liquidation preference	$ 828	$ 828