Stockholders' Equity (Details 3) - Stock options - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 746,499	$ 381,009	$ 2,129,172	$ 973,354
Research and development
Stock-Based Compensation Expense
Total stock-based compensation expense	220,748	148,244	856,671	483,677
General and administrative
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 525,751	$ 232,765	$ 1,272,501	$ 489,677