Stockholders' Equity - Changes in stockholders' equity (Details) (USD $)	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 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	(9,320,764)	(6,479,554)	(17,897,143)		(13,062,656)	31,900,000	27,500,000	47,000,000
Other comprehensive loss	(43,441)	(80,543)	(82,096)		(4,040)
Stock based compensation			999,123
Public offering common stock, net			(137,468)	[1]
Exercise of warrants			9,051,810	[2]
Stock dividend
Balance at June 30, 2013	6,964,529		6,964,529			15,030,303
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012			384,048
Balance at December 31, 2012 (in shares)			38,404,764
Net Loss
Other comprehensive loss
Stock based compensation			15,309
Stock based compensation (in shares)			1,530,883
Public offering common stock, net			217,118	[1]
Public offering common stock, net (in shares)			21,711,800	[1]
Exercise of warrants			189,964	[2]
Exercise of warrants (in shares)			18,996,400	[2]
Stock dividend			393
Stock dividend (in shares)			39,324
Balance at June 30, 2013	806,832		806,832
Balance at June 30, 2013 (in shares)	80,683,171		80,683,171
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			983,814
Public offering common stock, net			(354,586)	[1]
Exercise of warrants			8,861,846	[2]
Stock dividend			16,910
Balance at June 30, 2013	811,348,475		811,348,475
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			(82,096)
Stock based compensation
Public offering common stock, net				[1]
Exercise of warrants				[2]
Stock dividend
Balance at June 30, 2013	922,316		922,316
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012			(1,552,382)
Balance at December 31, 2012 (in shares)			165,906
Net Loss
Other comprehensive loss
Stock based compensation
Stock based compensation (in shares)
Public offering common stock, net				[1]
Public offering common stock, net (in shares)				[1]
Exercise of warrants				[2]
Stock dividend
Balance at June 30, 2013	(1,552,382)		(1,552,382)
Balance at June 30, 2013 (in shares)	165,906		165,906
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2012			(786,646,266)
Net Loss			(17,897,143)
Other comprehensive loss
Stock based compensation
Public offering common stock, net				[1]
Exercise of warrants				[2]
Stock dividend			(17,303)
Balance at June 30, 2013	$ (804,560,712)		$ (804,560,712)

[1] As discussed further below, the Company offered common stock and warrants in connection with its 2013 public offerings. The associated warrants have been separately valued and classified as a liability on the accompanying consolidated balance sheet. After consideration of the fair value ascribed to the warrants and the net proceeds of the overall offering, it was determined that the fair value of the warrants and the common stock exceeded the net proceeds received as part of the offering and consequently additional paid-in capital was reduced by $354,586.

[2] Pursuant to the exercise of warrants, additional paid-in capital was increased by $2,659,496 from the issuance of 18,996,400 shares of common stock. Additionally, paid-in capital was increased by $6,202,350 and warrant liability was reduced by $6,202,350 (the fair value of the warrants on the exercise date).