Stock-Based Compensation - Service Based Stock Options (Details) - USD ($)	1 Months Ended	6 Months Ended		12 Months Ended
	Apr. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Shares Underlying Options
Granted (in shares)		199,938
Exercised (in shares)		(30,000)
Forfeited (in shares)		(3,650)
Weighted Average Exercise Price
Exercised (in dollars per share)	$ 5.25	$ 4.93
Stock option awards - Service based awards
Shares Underlying Options
Outstanding at the beginning of the period (in shares)		7,856,480	6,906,001	6,906,001
Granted (in shares)		523,105
Exercised (in shares)		(30,000)
Forfeited (in shares)		(550,549)	(100,000)
Outstanding at the end of the period (in shares)		7,799,036	6,806,001	7,856,480	6,906,001
Exercisable, Shares underlying		6,183,193	6,578,161
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)		$ 7.50	$ 7.92	$ 7.92
Granted (in dollars per share)		4.33
Exercised (in dollars per share)		4.93
Forfeited (in dollars per share)		6.67	6.93
Outstanding at the end of the period (in dollars per share)		7.36	7.93	$ 7.50	$ 7.92
Exercise price (in dollars per share)		$ 8.16	$ 7.93
Weighted Average Remaining Contractual Term
Outstanding, Weighted Average Remaining Contractual Term		5 years 4 months 24 days	4 years 7 months 6 days	5 years 2 months 12 days	5 years
Granted, Weighted Average Remaining Contractual Term		9 years 8 months 12 days
Exercisable, Weighted Average Remaining Contractual Term		4 years 3 months 18 days	4 years 6 months
Aggregate intrinsic Value
Outstanding (in dollars)		$ 2,500	$ 629,680		$ 976,335
Intrinsic Value (in dollars)			$ 629,680