Summary of Significant Accounting Policies (Schedule of Share-based Compensation Expense) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 304,672	$ 439,205	$ 957,261	$ 1,499,910
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	105,796	107,199	268,289	351,342
General and Administrative Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 198,876	$ 332,006	$ 688,972	$ 1,148,568