Derivative Financial Instruments - Components of Derivative Liabilities (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative liabilities	$ 4,020,014	$ 5,356,203
Common shares linked to derivative liabilities	6,782,859	8,059,843
Warrant Derivatives [Member]
Derivative [Line Items]
Derivative liabilities	3,166,050	3,826,620
Common shares linked to derivative liabilities	3,812,500	3,812,500
Senior Convertible Notes [Member] | Compound Embedded Derivative [Member]
Derivative [Line Items]
Derivative liabilities	853,964	1,529,583
Common shares linked to derivative liabilities	2,970,359	4,247,343
Senior Convertible Notes [Member] | Warrant Derivatives [Member]
Derivative [Line Items]
Derivative liabilities	1,638,750	1,921,094
Common shares linked to derivative liabilities	1,562,500	1,562,500
Series G Convertible Preferred Stock [Member] | Warrant Derivatives [Member]
Derivative [Line Items]
Derivative liabilities	$ 1,527,300	$ 1,905,526
Common shares linked to derivative liabilities	2,250,000	2,250,000