Note 8 - Net Loss Per Share - Schedule of Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of potential common shares excluded (in shares)	4,611,845	90,708
Share-based Payment Arrangement, Option [Member]
Number of potential common shares excluded (in shares)	783,383	14,473
Series B Convertible Preferred Stock [Member]
Number of potential common shares excluded (in shares)	458,994
Warrant [Member]
Number of potential common shares excluded (in shares)	3,369,468	76,235