Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Stock-based compensation	$ 5,561,895	$ 6,625,743	$ 5,646,852
Stock options
Stock-Based Compensation
Stock-based compensation	5,538,102	6,376,121	5,407,012
Stock options | Research and development
Stock-Based Compensation
Stock-based compensation	2,348,205	2,884,689	2,127,386
Stock options | General and administrative
Stock-Based Compensation
Stock-based compensation	3,189,897	3,491,432	3,279,626
Restricted stock
Stock-Based Compensation
Stock-based compensation	23,793	249,622	239,840
Restricted stock | Research and development
Stock-Based Compensation
Stock-based compensation	$ 23,793	202,809	157,480
Restricted stock | General and administrative
Stock-Based Compensation
Stock-based compensation		$ 46,813	$ 82,360