Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit
Balance at Dec. 31, 2016	$ (193,824)			$ 26,005		$ (219,829)
Balance, Shares at Dec. 31, 2016	80,844,138	80,844,138
Balance at Dec. 31, 2016	$ 213,180	$ 213,180
Balance, Shares at Dec. 31, 2016			4,818,812
Issuance of common stock upon exercise of stock options	1,443		$ 1	1,442
Issuance of common stock upon exercise of stock options			445,995
Share repurchases	(671)				$ (671)
Share repurchases, shares			(92,637)
Vesting of early exercised stock options	12			12
Issuance of common stock pursuant to acquisition			108,332
Issuance of common stock shares upon expiration of warrants			357,283
Stock-based compensation expense	7,517			7,517
Net loss	(70,450)					(70,450)
Balance at Sep. 30, 2017	$ (255,973)		$ 1	$ 34,976	$ (671)	$ (290,279)
Balance, shares at Sep. 30, 2017	80,844,138	80,844,138
Balance at Sep. 30, 2017	$ 213,180	$ 213,180
Balance, Shares at Sep. 30, 2017			5,637,785