Note 11 - Stock Options and Restricted Stock - Potentially Dilutive Instruments (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Potentially dilutive instruments (in shares)	1,381,508	214,969	1,341,209	245,489
Share-Based Payment Arrangement, Option [Member]
Potentially dilutive instruments (in shares)	3,471	103,503	4,845	110,840
Restricted Stock [Member]
Potentially dilutive instruments (in shares)	1,193,887	43,667	1,159,082	43,667
Warrant [Member]
Potentially dilutive instruments (in shares)	184,150	67,799	177,282	90,983