Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	5,452,523	4,733,034
Stock Option
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	1,033,274	90,167
Warrants
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	4,404,185	3,698,256
Restricted Stock Units (RSUs)
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	14,187	2,067
Series A Preferred Stock | Convertible Preferred Stock
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	877	877
Series B Preferred Stock | Convertible Preferred Stock
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	0	941,667