Note 9 - Loss Per Share - Antidilutive Securities Excluded from the Diluted Calculations (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities (in shares)	818,117	729,975
Warrant [Member]
Antidilutive Securities (in shares)	7,257,883	2,025,971
Convertible Debt Securities [Member]
Antidilutive Securities (in shares)	574,367	130,307
Series B Convertible Preferred Stock [Member]
Antidilutive Securities (in shares)	79,246	79,246
Series D Convertible Preferred Stock [Member]
Antidilutive Securities (in shares)		350,004
Series E Convertible Preferred Stock [Member]
Antidilutive Securities (in shares)		1,484,634