Stock-Based Compensation - Share-based compensation expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 1,501,326	$ 1,365,332	$ 3,018,628	$ 1,811,335
Service based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	974,611	1,365,332	1,970,986	1,811,335
Restricted stock awards - Service based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense		1,012,171		1,271,902
Restricted stock units - Service based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	427,472		771,823
Stock option awards - Service based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	547,139	353,161	1,199,163	539,433
Performance based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	526,715		1,047,642
Restricted stock units - Performance based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	402,814	0	801,202	0
Stock option awards - Performance based awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 123,901	$ 0	$ 246,440	$ 0