Net Loss per Share - Reconciliation of Numerator and Denominator Used in Computing Basic and Diluted Net Loss per Share (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss	$ (18,960,017)	$ (26,039,550)
Denominator:
Weighted-average shares outstanding-basic and diluted	10,597,318	7,113,075
Net loss per share, basic and diluted	$ (1.79)	$ (3.66)