Basis of Presentation and Significant Accounting Policies - Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended		6 Months Ended		138 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 44,888	$ 45,090	$ 86,640	$ 90,180	$ 6,048,840
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	21,612	18,303	40,375	36,605
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 23,276	$ 26,787	$ 46,265	$ 53,575