Condensed Statements of Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5,380,846)	$ (6,488,442)	$ (17,038,022)	$ (20,366,469)
Other comprehensive income, net of tax effect:
Unrealized gain (loss) on short and long-term investments	0	(2,836)	1,090	41,037
Comprehensive loss	$ (5,380,846)	$ (6,491,278)	$ (17,036,932)	$ (20,325,432)