Condensed Consolidated Statement of Stockholders' Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Stockholders Equity, Beginning Balance at Dec. 31, 2016	$ 103,248	$ 30	$ 685,272	$ (582,054)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2016		30,370,946
Issuance of common stock for exercise of stock options	23		23
Issuance of common stock for exercise of stock options, Shares		49,861
Stock-based compensation	4,498		4,498
Issuance of common stock, net of offering costs of $2.1 million	27,422	$ 22	27,400
Issuance of common stock, net of offering costs of $2.1 million, shares		21,847,636
Net loss	(31,416)			(31,416)
Stockholders Equity, Ending Balance at Sep. 30, 2017	$ 103,775	$ 52	717,201	(613,478)
Stockholders Equity, Ending Balance, Shares at Sep. 30, 2017		52,268,443
Cumulative effect of adoption of new accounting standard			$ 8	$ (8)