Stockholders' Equity - Changes in stockholders' equity (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012	$ 15,030,303
Net loss	(8,576,379)		(6,583,102)	(31,900,000)	(27,500,000)	(47,000,000)
Other comprehensive loss	(38,655)		76,503
Stock based compensation	513,722
Public offering common stock, net	(137,468)
Exercise of warrants	918,512	[1]
Balance at March 31, 2013	7,710,035			15,030,303
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012	384,048
Balance at December 31, 2012 (shares)	38,404,764
Net loss
Other comprehensive loss
Stock based compensation	7,902
Stock based compensation (shares)	790,233
Public offering common stock, net	217,118
Public offering common stock, net (shares)	21,711,800
Exercise of warrants	29,000	[1]
Exercise of warrants (Shares)	2,900,000	[1]
Balance at March 31, 2013	638,068
Balance at March 31, 2013 (shares)	63,806,797
Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012	801,840,491
Net loss
Other comprehensive loss
Stock based compensation	505,820
Stock based compensation (shares)
Public offering common stock, net	(354,586)
Public offering common stock, net (shares)
Exercise of warrants	889,512	[1]
Balance at March 31, 2013	802,881,237
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012	1,004,412
Net loss
Other comprehensive loss	(38,655)
Stock based compensation
Stock based compensation (shares)
Public offering common stock, net
Public offering common stock, net (shares)
Exercise of warrants		[1]
Balance at March 31, 2013	965,757
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012	(1,552,382)
Balance at December 31, 2012 (shares)	165,906
Net loss
Other comprehensive loss
Stock based compensation
Stock based compensation (shares)
Public offering common stock, net
Public offering common stock, net (shares)
Exercise of warrants		[1]
Balance at March 31, 2013	(1,552,382)
Balance at March 31, 2013 (shares)	165,906
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012	(786,646,266)
Net loss	(8,576,379)
Other comprehensive loss
Stock based compensation
Stock based compensation (shares)
Public offering common stock, net
Public offering common stock, net (shares)
Exercise of warrants		[1]
Balance at March 31, 2013	$ (795,222,645)

[1] Pursuant to the exercise of the warrants, additional paid-in capital was increased by $406,000 from the issuance of 2,900,000 shares of common stock. Additionally, paid-in capital was increased by $483,512 and warrant liability was reduced by $483,512, the fair value of the warrants on the exercise date.