Net Loss per Common Share - Computation of Basic and Diluted Net Loss per Common Share (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic and diluted net loss per common share:
Net loss	$ (18,326,992)	$ (32,484,146)	$ (13,762,214)	$ (10,640,376)	$ (50,811,138)	$ (24,402,590)
Weighted average common shares outstanding, basic and diluted	37,100,770		33,801,749		37,081,064	33,429,178
Net loss per common share, basic and diluted	$ (0.49)		$ (0.41)		$ (1.37)	$ (0.73)