CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - 6 months ended Jun. 30, 2018 - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balance at beginning of period at Dec. 31, 2017		$ 384,943	$ (246)	$ (159,435)	$ 225,262
Balance at beginning of period (in shares) at Dec. 31, 2017	30,856,505				30,856,505
Increase (Decrease) in Stockholders' Equity
Exercise of stock options and vesting of RSUs		(62)			$ (62)
Exercise of stock options and vesting of RSUs, shares	108,791
Unrealized gain on marketable securities			46		46
Foreign currency translation adjustment			12		12
Stock-based compensation expense		10,392			10,392
Net loss				(61,447)	(61,447)
Balance at end of period at Jun. 30, 2018		$ 395,273	$ (188)	$ (220,882)	$ 174,203
Balance at end of period (in shares) at Jun. 30, 2018	30,965,296				30,965,296