Note 10 - Stock Options and Restricted Stock - Potentially Dilutive Instruments (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Potentially dilutive instruments (in shares)	1,300,463	274,341
Share-based Payment Arrangement, Option [Member]
Potentially dilutive instruments (in shares)	6,235	118,143
Restricted Stock [Member]
Potentially dilutive instruments (in shares)	170,338	112,531
Warrant [Member]
Potentially dilutive instruments (in shares)	1,123,890	43,667