Derivative Instruments (Details 1) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Changes in derivative warrant liability
Balance at December 31			$ 35,473,230	$ 10,647,190
Decrease in the fair value of the warrants	(4,954,238)	(1,162,897)	(10,567,444)	(1,282,244)
Reduction in derivative liability due to exercise of warrants			(1,377,904)
Balance at June 30,	$ 23,527,882	$ 9,364,946	$ 23,527,882	$ 9,364,946