STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balances at Dec. 31, 2012	$ 130	$ 939,867	$ (854,384)	$ 40	$ 85,653
Balances (in shares) at Dec. 31, 2012	130,242,695
Increase (Decrease) in Stockholders' Equity
Net income (loss)			(38,379)		(38,379)
Other comprehensive loss				(54)	(54)
Stock-based compensation related to issuance of common stock and options in exchange for services		252			252
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)	66,853
Cancellations of non-vested restricted stock under equity plans, net of issuances of common stock		6,553			6,553
Cancellations of non-vested restricted stock under equity plans, net of issuances of common stock (in shares)	(388,056)
Stock-based compensation for equity-based awards to employees and directors		4,435			4,435
401(k) contribution	$ 1	1,296			1,297
401(k) contribution (in shares)	756,457
Balances at Dec. 31, 2013	$ 131	952,403	(892,763)	(14)	59,757
Balances (in shares) at Dec. 31, 2013	130,677,949
Increase (Decrease) in Stockholders' Equity
Net income (loss)			(35,670)		(35,670)
Other comprehensive loss				(70)	(70)
Issuance of common stock in connection with public offering, net of issuance costs of $6,695,000	$ 26	96,779			96,805
Issuance of common stock in connection with public offering, net of issuance costs (in shares)	25,875,000
Stock-based compensation related to issuance of common stock and options in exchange for services		253			253
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)	71,239
Issuance of common stock upon net exercise of warrants (in shares)	168,039
Issuances of common stock under equity plans, net of cancellations of non-vested restricted stock		1,555			1,555
Issuances of common stock under equity plans, net of cancellations of non-vested restricted stock (in shares)	564,950
Stock-based compensation for equity-based awards to employees and directors		7,658			7,658
401(k) contribution		424			424
401(k) contribution (in shares)	72,694
Balances at Dec. 31, 2014	$ 157	1,059,072	(928,433)	(84)	$ 130,712
Balances (in shares) at Dec. 31, 2014	157,429,871				157,429,871
Increase (Decrease) in Stockholders' Equity
Net income (loss)			46		$ 46
Other comprehensive loss				(129)	(129)
Stock-based compensation related to issuance of common stock and options in exchange for services		364			364
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)	18,077
Issuance of common stock upon exercise of warrants	$ 1	880			881
Issuance of common stock upon exercise of warrants (in shares)	235,000
Issuances of common stock under equity plans, net of cancellations of non-vested restricted stock	$ 1	1,693			1,694
Issuances of common stock under equity plans, net of cancellations of non-vested restricted stock (in shares)	1,098,411
Stock-based compensation for equity-based awards to employees and directors		8,397			8,397
401(k) contribution		161			161
Balances at Dec. 31, 2015	$ 159	$ 1,070,567	$ (928,387)	$ (213)	$ 142,126
Balances (in shares) at Dec. 31, 2015	158,781,359				158,781,359