Common Stock - Antidilutive shares (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	5,557,326	5,370,274
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	1,550,975	1,608,996
Options to purchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share (in shares)	4,006,351	3,761,278