CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Convertible Note 2023	Convertible Note 2023 Additional Paid-in Capital	Convertible Note 2019	Convertible Note 2019 Additional Paid-in Capital
Balance (in shares) at Dec. 31, 2017		53,400,281
Balance at Dec. 31, 2017	$ 44,753	$ 554	$ 106,312	$ (2,019)	$ (60,094)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation expense	1,654		1,654
Stock options exercised (in shares)		236,000
Stock options exercised	246	$ 2	244
Issuance of stock for vested restricted stock units (in shares)		101,607
Issuance of stock for vested restricted stock units		$ 1	(1)
Issuance of stock to consultant (in shares)		25,000
Issuance of stock to consultant	102		102
Fair value of conversion feature on Convertible 4.75% Senior Notes						$ 18,637	$ 18,637
Partial extinguishment of equity component of Convertible 3.75% Senior Notes	7,600							$ (7,602)	$ (7,602)
Cumulative translation adjustment	(224)			(224)
Net loss	(21,866)				(21,866)
Balance (in shares) at Sep. 30, 2018		53,762,888
Balance at Sep. 30, 2018	$ 35,700	$ 557	$ 119,346	$ (2,243)	$ (81,960)