Net Loss Per Common Share - Calculation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net loss	$ (21,081,808)	$ (9,940,658)	$ (57,636,873)	$ (25,313,037)
Denominator:
Weighted-average basic and diluted common shares (in shares)	24,166,113	7,504,148	20,958,421	7,042,977
Basic and diluted net loss per common share (in dollars per share)	$ (0.87)	$ (1.32)	$ (2.75)	$ (3.59)