UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF REDEEMABLE CONVERTIBLE AND CONVERTIBLE PREFERRED STOCK $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) shares
Increase (Decrease) in Redeemable Convertible and Convertible Preferred Stock
Exercise of stock options	$ 2,520
Ending balance (in shares) | shares	0
Redeemable convertible preferred stock
Increase (Decrease) in Redeemable Convertible and Convertible Preferred Stock
Beginning balance	$ 333,204
Beginning balance (in shares) | shares	88,741,194
Accretion of redeemable convertible preferred stock to redemption value	$ 199,492
Conversion of convertible preferred stock upon initial public offering	$ (532,696)
Conversion of convertible preferred stock upon initial public offering (in shares) | shares	(88,741,194)
Ending balance	$ 0
Ending balance (in shares) | shares	0
Series A convertible preferred stock
Increase (Decrease) in Redeemable Convertible and Convertible Preferred Stock
Beginning balance	$ 1,510
Beginning balance (in shares) | shares	3,851,806
Exercise of stock options	$ 211
Exercise of stock options (in shares) | shares	360,385
Conversion of convertible preferred stock upon initial public offering	$ (1,721)
Conversion of convertible preferred stock upon initial public offering (in shares) | shares	(4,212,191)
Ending balance	$ 0
Ending balance (in shares) | shares	0