Note 9 - Stock Options and Restricted Stock - Potentially Dilutive Instruments (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Potentially dilutive instruments (in shares)	1,376,569	245,648	1,353,125	245,542
Share-based Payment Arrangement, Option [Member]
Potentially dilutive instruments (in shares)	2,934	98,823	4,201	106,805
Restricted Stock [Member]
Potentially dilutive instruments (in shares)	181,550	27,071	178,720	69,523
Warrant [Member]
Potentially dilutive instruments (in shares)	1,192,085	119,754	1,170,204	69,214