CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (14,795,763)	$ (6,527,568)	$ (38,213,561)	$ (18,085,115)
Other comprehensive gain:
Change in unrealized gain on available for sale securities, net	27,768		52,430
Total other comprehensive gain	27,768		52,430
Comprehensive loss	$ (14,767,995)	$ (6,527,568)	$ (38,161,131)	$ (18,085,115)