CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - 6 months ended Jun. 30, 2017 - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance as of beginning of the period at Dec. 31, 2016	$ 46	$ 435,551	$ (204,726)	$ (1)	$ 230,870
Balance as of beginning of the period (in shares) at Dec. 31, 2016	46,201,563
Stockholders' Equity
Exercise of stock options	$ 1	4,315			4,316
Exercise of stock options (in shares)	479,339
Exercise of warrants (in shares)	138,903
Issuance of common stock under employee stock purchase plan		1,265			1,265
Issuance of common stock under employee stock purchase plan (in shares)	90,968
Equity component of Convertible Senior Notes, net of debt issuance costs		62,404			62,404
Stock-based compensation		7,731	(69)		7,662
Follow-on Offering	$ 8	123,920			123,928
Follow-on Offering (in shares)	7,887,500
Net loss			(31,069)		(31,069)
Balance as of end of the period at Jun. 30, 2017	$ 55	$ 635,186	$ (235,864)	$ (1)	$ 399,376
Balance as of end of the period (in shares) at Jun. 30, 2017	54,798,273