Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Oct. 31, 2009 October 2009 Offering [Member]
Derivatives, Fair Value [Line Items]
Short term investments	$ 0		$ 0		$ 15,433,967
Common stock, shares authorized under plan, in shares	87,737,329		87,737,329		87,543,781	10,900,000
Warrants to purchase common stock, in shares						5,450,000
Change in fair value of stock warrants	$ (154,746)	$ 205,700	$ 50,026	$ 6,465,067