Condensed Statements of Comprehensive Loss - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5,840,902)	$ (6,851,603)	$ (11,657,176)	$ (13,878,027)
Other comprehensive income, net of tax effect:
Unrealized gain on short and long-term investments	736	4,522	1,090	43,873
Comprehensive loss	$ (5,840,166)	$ (6,847,081)	$ (11,656,086)	$ (13,834,154)