Net Loss per Share - Numerator and Denominator Used in Computing Basic and Diluted Net Loss per Share (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net loss	$ (5,840,902)	$ (6,851,603)	$ (11,657,176)	$ (13,878,027)
Denominator:
Weighted-average shares outstanding-basic and diluted	9,769,322	7,018,502	8,875,177	6,952,012
Net loss per share, basic and diluted	$ (0.60)	$ (0.98)	$ (1.31)	$ (2.00)