Statements of Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (26,039,550)	$ (21,397,791)
Other comprehensive income (loss), net of tax effect:
Unrealized gain (loss) on short and long-term investments	40,267	(41,357)
Comprehensive loss	(25,999,283)	(21,439,148)
Less: Accretion of stock issuance costs		(35,046)
Less: Accretion of Series E warrant discount		(127,616)
Less: Accretion of Series D and E redeemable convertible preferred stock dividends		(1,165,932)
Comprehensive loss attributable to common stockholders	$ (25,999,283)	$ (22,767,742)