Stock Options, Stock-Based Compensation Expense (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock-Based Compensation [Abstract]
Stock-based compensation expense	$ 1,570,914	$ 1,233,031	$ 4,637,142	$ 4,029,326
Research and Development [Member]
Stock-Based Compensation [Abstract]
Stock-based compensation expense	702,284	567,452	2,090,076	1,609,683
General and Administrative [Member]
Stock-Based Compensation [Abstract]
Stock-based compensation expense	$ 868,630	$ 665,579	$ 2,547,066	$ 2,419,643