CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (UNAUDITED) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (12,894,236)	$ (6,002,754)	$ (23,417,798)	$ (11,557,547)
Other comprehensive gain:
Change in unrealized gain on available for sale securities, net	37,519		24,662
Total other comprehensive gain	37,519		24,662
Comprehensive loss	$ (12,856,717)	$ (6,002,754)	$ (23,393,136)	$ (11,557,547)