Consolidated Statements of Changes in Redeemable Convertible Preferred Stock shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) shares
Beginning balance	$ 97,963
Accretion of redeemable convertible preferred stock	6,258
Issuance of preferred stock upon exercise of preferred stock warrants	1,863
Conversion of preferred stock into common stock at initial public offering	(106,084)
Series 1
Beginning balance	$ 60,184
Beginning balance | shares	5,334
Accretion of redeemable convertible preferred stock	$ 6,258
Conversion of preferred stock into common stock at initial public offering	$ (66,442)
Conversion of preferred stock into common stock at initial public offering, shares | shares	(5,334)
Series 2
Beginning balance	$ 37,779
Beginning balance | shares	2,552
Issuance of preferred stock upon exercise of preferred stock warrants	$ 1,863
Issuance of preferred stock upon exercise of preferred stock warrants, shares | shares	106
Conversion of preferred stock into common stock at initial public offering	$ (39,642)
Conversion of preferred stock into common stock at initial public offering, shares | shares	(2,658)