Note 2 - Summary of Significant Accounting Policies - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities (in shares)	3,721,024	2,218,693
Common Stock Options [ member]
Antidilutive Securities (in shares)	7,549	7,179
Preferred Stock [Member]
Antidilutive Securities (in shares)	45,015	41,398
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities (in shares)	471,252	92,245
Common Stock Warrants [Member]
Antidilutive Securities (in shares)	3,197,208	2,077,871