Income Taxes - Difference in Actual Income Tax Expense Computed by Applying the Statutory Federal Income Tax Rate to Loss Before Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Computed tax (benefit) at 34%	$ (6,445,413)	$ (8,850,007)
State taxes, net of federal benefit	(532,952)	(462,609)
Stock-based compensation	231,396	210,367
Expiring state NOL carryforwards		94,962
Return to provision	(15,375)	248,263
Other	20,292	25,718
Federal rate change on deferred items as of enactment date	16,232,211
Change in valuation reserve	(8,470,655)	9,538,280
Total income tax expense	2,921	10,118
State
Income Tax Disclosure [Line Items]
Research and development tax credit	(576,525)	(453,071)
Federal
Income Tax Disclosure [Line Items]
Research and development tax credit	$ (440,058)	$ (341,785)