Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($)		12 Months Ended
	Jul. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Stock-Based Compensation
Stock-based compensation		$ 3,269,366	$ 1,600,625
Research and Development
Stock-Based Compensation
Stock-based compensation		1,281,108	545,901
General and Administrative
Stock-Based Compensation
Stock-based compensation		1,988,258	1,054,724
Stock options
Stock-Based Compensation
Stock-based compensation		3,029,526	1,263,676
Stock options | Research and Development
Stock-Based Compensation
Stock-based compensation		1,137,639	403,395
Stock options | General and Administrative
Stock-Based Compensation
Stock-based compensation		1,891,887	860,281
Restricted stock
Stock-Based Compensation
Stock-based compensation		239,840	336,949
Restricted stock | Research and Development
Stock-Based Compensation
Stock-based compensation		143,469	142,506
Restricted stock | General and Administrative
Stock-Based Compensation
Stock-based compensation		$ 96,371	$ 194,443
2014 Plan | Stock options
Stock-Based Compensation
Stock-based compensation	$ 0
2014 Plan | Restricted stock
Stock-Based Compensation
Stock-based compensation	$ 0