Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	17,805,051	5,452,523
Options to purchase Common Stock
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	1,924,039	1,033,274
Warrants to purchase Common Stock
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	12,329,435	4,404,185
Restricted Stock Units
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	2,241	14,187
Series A 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 E Convertible Preferred Stock
Net Loss Per Share
Antidilutive securities excluded from the calculation of basic and diluted loss per share (in shares)	3,548,459	0