Note 3 - Basis of Presentation and Summary of Significant Accounting Policies - Outstanding Dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Anti-dilutive securities (in shares)	2,343,069	2,331,828
Convertible Debt Securities [Member]
Anti-dilutive securities (in shares)		14,325
Warrant [Member]
Anti-dilutive securities (in shares)	2,087,012	2,113,815
Share-based Payment Arrangement, Option [Member]
Anti-dilutive securities (in shares)	256,057	203,586
Restricted Stock [Member]
Anti-dilutive securities (in shares)		102