Note 9 - Net Loss Per Share - Schedule of Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Number of potential common shares excluded (in shares)	5,569,028	4,611,845
Share-based Payment Arrangement, Option [Member]
Number of potential common shares excluded (in shares)	4,308,383	783,383
Series B Convertible Preferred Stock [Member]
Number of potential common shares excluded (in shares)	190,617	458,994
Warrant [Member]
Number of potential common shares excluded (in shares)	1,070,028	3,369,468