Stock Options, Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Unamortized Stock Compensation Expense [Abstract]
Unamortized stock compensation expense	$ 8,725,126
Stock Options [Member]
Number of Shares [Roll Forward]
Options outstanding, beginning balance (in shares)	6,462,795	5,316,511
Granted (in shares)	2,322,906	1,365,400
Exercised (in shares)	(198,300)	(35,366)
Forfeited (in shares)	(1,543,576)	(183,750)
Options outstanding, ending balance (in shares)	7,043,825	6,462,795
Vested and expected to vest (in shares)	7,043,825	6,462,795
Exercisable (in shares)	5,001,465	4,066,066
Weighted Average Exercise Price [Roll Forward]
Options outstanding, beginning balance (in dollars per share)	$ 6.50	$ 5.84
Granted (in dollars per share)	7.52	9.39
Exercised (in dollars per share)	3.64	3.34
Forfeited (in dollars per share)	10.30	9.46
Options outstanding, ending balance (in dollars per share)	6.09	6.50
Vested and expected to vest (in dollars per share)	6.09	6.50
Exercisable (in dollars per share)	$ 5.71	$ 5.14
Remaining Contractual Life and Aggregate Intrinsic Value [Abstract]
Options outstanding, weighted average remaining contractual life	5 years 10 months 2 days	7 years 1 month 17 days
Options outstanding, aggregate intrinsic value	$ 3,977	$ 20,467,335
Vested and expected to vest, weighted average contractual life	5 years 10 months 2 days	7 years 1 month 17 days
Vested and expected to vest, aggregate intrinsic value	$ 3,977	$ 20,467,335
Exercisable, weighted average contractual life	5 years 8 months 1 day	6 years 2 months 16 days
Exercisable, aggregate intrinsic value	$ 3,977	$ 18,100,589
Unamortized Stock Compensation Expense [Abstract]
Period for recognition	2 years 6 months 7 days