CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - 9 months ended Sep. 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		24			$ 24
Exercise of stock options and vesting of RSUs, shares	134,555
Unrealized gain on marketable securities			111		111
Foreign currency translation adjustment			19		19
Stock-based compensation expense		15,099			15,099
Net loss				(94,187)	(94,187)
Balance at end of period at Sep. 30, 2018		$ 400,066	$ (116)	$ (253,622)	$ 146,328
Balance at end of period (in shares) at Sep. 30, 2018	30,991,060				30,991,060