Stock Options, Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Unamortized Stock Compensation Expense [Abstract]
Unamortized stock compensation expense | $	$ 15,319,731
Period for recognition	1 year 11 months 19 days
Stock Options [Member]
Number of Shares [Roll Forward]
Options outstanding, beginning balance (in shares) | shares	6,462,795
Granted (in shares) | shares	2,322,906
Exercised (in shares) | shares	(198,300)
Forfeited (in shares) | shares	(1,194,835)
Options outstanding, ending balance (in shares) | shares	7,392,566
Vested and expected to vest (in shares) | shares	7,392,566
Exercisable (in shares) | shares	4,183,685
Weighted Average Exercise Price [Roll Forward]
Options outstanding, beginning balance (in dollars per share) | $ / shares	$ 6.50
Granted (in dollars per share) | $ / shares	7.52
Exercised (in dollars per share) | $ / shares	3.64
Forfeited (in dollars per share) | $ / shares	10.35
Options outstanding, ending balance (in dollars per share) | $ / shares	6.28
Vested and expected to vest (in dollars per share) | $ / shares	6.28
Exercisable (in dollars per share) | $ / shares	$ 5.54
Weighted Average Remaining Contractual Life and Aggregate Intrinsic Value [Abstract]
Options outstanding, weighted average remaining contractual life	6 years 5 months 5 days
Vested and expected to vest, weighted average remaining contractual life	6 years 5 months 5 days
Exercisable, weighted average remaining contractual life	6 years 4 days
Options outstanding, aggregate intrinsic value | $	$ 107,730
Vested and expected to vest, aggregate intrinsic value | $	107,730
Exercisable, aggregate intrinsic value | $	$ 107,730