Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Accumulated Deficit [Member]	Convertible Preferred Stock [Member]
Beginning balance at Dec. 31, 2012	$ 10,292,000	$ 4,000	$ 272,231,000	$ (261,944,000)	$ 1,000
Beginning balance, Shares at Dec. 31, 2012		4,193,690			564,642
Issuance of common stock (net of costs)	8,695,000	$ 7,000	8,688,000
Issuance of common stock (net of costs), Shares		7,189,503
Conversion of preferred stock to common stock		$ 1,000			$ (1,000)
Conversion of preferred stock to common stock, Shares		196,422			(235,717)
Cancellation of shares from reverse stock split		(2,865)
Stock-based compensation	492,000		492,000
Stock-based compensation, Shares		58,200
Net loss	(12,173,000)			(12,173,000)
Ending balance at Dec. 31, 2013	7,306,000	$ 12,000	281,411,000	(274,117,000)
Ending balance, Shares at Dec. 31, 2013		11,634,950			328,925
Issuance of common stock (net of costs) from exercise of outstanding warrants	4,085,000	$ 2,000	4,083,000
Issuance of common stock (net of costs) from exercise of outstanding warrants, Shares		1,589,471
Stock-based compensation	862,000		862,000
Stock-based compensation, Shares		1,039,620
Net loss	(8,251,000)			(8,251,000)
Ending balance at Dec. 31, 2014	4,002,000	$ 14,000	286,356,000	(282,368,000)
Ending balance, Shares at Dec. 31, 2014		14,264,041			328,925
Issuance of common stock (net of costs)	8,890,000	$ 17,000	8,873,000
Issuance of common stock (net of costs), Shares		16,594,784
Issuance of Series B preferred stock	4,305,000		4,305,000
Issuance of Series B preferred stock, Shares					4,750
Issuance of common stock (net of costs) from exercise of outstanding warrants	1,687,000	$ 1,000	1,686,000
Issuance of common stock (net of costs) from exercise of outstanding warrants, Shares		916,858
Reclassification of warrant liability upon exercise	669,000		669,000
Conversion of preferred stock to common stock	0	$ 8,000	(8,000)
Conversion of preferred stock to common stock, Shares		8,006,429			(2,802)
Repurchase of common shares to satisfy withholding obligations	(27,000)	$ (1,000)	(26,000)
Repurchase of common shares to satisfy withholding obligations, Shares		(133,894)
Stock-based compensation	2,198,000		2,198,000
Stock-based compensation, Shares		(40,000)
Net loss	(8,602,000)			(8,602,000)
Ending balance at Dec. 31, 2015	$ 13,122,000	$ 39,000	$ 304,053,000	$ (290,970,000)
Ending balance, Shares at Dec. 31, 2015		39,608,218			330,873