Stockholders' Equity (Details)		3 Months Ended
	Jun. 03, 2019	Mar. 31, 2020 Vote shares	Dec. 31, 2019 shares
Stockholders' Equity
Number of voting rights entitled for each share of common stock held | Vote		1
Reverse stock split ratio	0.015
Shares of common stock reserved for issuance
Options issued and outstanding		4,508,021	3,902,675
Options available for grant under stock option plans		160,697	479,829
RSUs awards issued and outstanding		5,613	5,613
Warrants issued and outstanding		17,622,930	19,421,892
Convertible warrants		9,580
Total		28,625,610	27,200,498
Inducement options issued and outstanding
Shares of common stock reserved for issuance
Options issued and outstanding		74	74
Blank check preferred stock
Stockholders' Equity
Common stock, shares authorized		10,000,000
Series A convertible preferred stock
Shares of common stock reserved for issuance
Convertible warrants		473,565	473,565
Series B convertible preferred stock
Shares of common stock reserved for issuance
Convertible warrants		4,423,250	985,500
Series B-2 convertible preferred stock
Shares of common stock reserved for issuance
Convertible warrants		1,431,460	1,931,350
Common Stock
Stockholders' Equity
Common stock, shares authorized		210,000,000
Common Stock | Common stock - voting
Stockholders' Equity
Common stock, shares authorized		150,000,000	150,000,000
Common Stock | Common stock - non-voting
Stockholders' Equity
Common stock, shares authorized		50,000,000	50,000,000
Convertible non-voting common stock
Stockholders' Equity
Reverse stock split ratio		1,050