Stock Purchase Warrants (Details) (USD $)	3 Months Ended		9 Months Ended		294 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	0 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013 January 2010 Class A Warrants	Dec. 31, 2012 January 2010 Class A Warrants	Sep. 30, 2013 December 2010 Warrants	Dec. 31, 2012 December 2010 Warrants	Sep. 24, 2013 August 2013 warrants item	Sep. 30, 2013 August 2013 warrants	Apr. 17, 2013 October 2007 Warrants	Oct. 17, 2007 October 2007 Warrants
Stock Purchase Warrants
Number of warrants issued													740,131
Exercise price per share (in dollars per share)						$ 1.27		$ 0.28		$ 0.375	$ 0.375	$ 12.72
Warrants outstanding						6,034,637		308,100			22,667,000
Total shares issuable on exercise						4,525,978		308,100		7,333,000	22,667,000
Number of warrant holders										2
Cash paid for warrant exercise										$ 1,209,945
Net proceeds from exercise of warrants										1,470,000
Net proceeds raised from sale of shares under ATM			3,337,000
Assumptions used in calculating the estimated fair value of the warrants
Closing stock price (in dollars per share)						$ 0.28	$ 1.26	$ 0.28	$ 1.26		$ 0.28
Expected dividend rate (as a percent)						0.00%	0.00%	0.00%	0.00%		0.00%
Expected stock price volatility (as a percent)						78.80%	74.00%	73.00%	70.10%		80.10%
Risk-free interest rate (as a percent)						0.30%	0.40%	0.40%	0.40%		1.60%
Expected life						1 year 9 months	2 years 6 months	2 years 2 months 16 days	2 years 11 months 16 days		4 years 10 months 17 days
Change in the estimated fair value of warrant liabilities
Balance at the beginning of the period			1,995,000
Warrant issuance			5,874,000
Warrant exercise			(513,000)
Decrease in fair value of warrants	(1,367,000)	(2,241,000)	(3,331,000)	(3,289,000)	(19,868,000)
Balance at the end of the period	$ 4,025,000		$ 4,025,000		$ 4,025,000