Summary of Significant Accounting Policies - Net Loss Per Share (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Numerator: Net loss attributable to common shareholders	$ (4,131,363)	$ (6,522,548)	$ (8,310,463)	$ (11,314,785)
Net loss used for diluted loss per share	$ (4,131,363)	$ (6,522,548)	$ (8,310,463)	$ (11,314,785)
Denominator for basic and diluted net loss per share:
Weighted-average shares used to compute basic loss per share (in shares)	5,241,924	1,237,244	4,667,434	1,004,391
Weighted-average shares used to compute diluted net loss per share (in shares)	5,241,924	1,237,244	4,667,434	1,004,391
Net loss per share attributable to common stockholders:
Net loss per common share - basic (in USD per share)	$ (0.79)	$ (5.27)	$ (1.78)	$ (11.27)
Net loss per common share - diluted (in USD per share)	$ (0.79)	$ (5.27)	$ (1.78)	$ (11.27)