Note 8 - Loss Per Share - Antidilutive Securities Excluded from the Diluted Calculations (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities (in shares)	794,038	407,158
Warrant [Member]
Antidilutive Securities (in shares)	5,663,594	595,113
Convertible Debt Securities [Member]
Antidilutive Securities (in shares)	378,000	504,770
Series B Convertible Preferred Stock [Member]
Antidilutive Securities (in shares)	7,925	7,925
Series D Convertible Preferred Stock [Member]
Antidilutive Securities (in shares)	350,000
Series E Convertible Preferred Stock [Member]
Antidilutive Securities (in shares)	691,159