Note 2 - Summary of Significant Accounting Policies - Weighted Average Common Shares (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Weighted average common shares outstanding - basic (in shares)	10,496,188	10,269,995	10,422,851	10,247,779
Unvested shares of restricted stock and employee stock options (in shares)	296,102	17,567	271,500	0
Weighted average common shares and common share equivalents outstanding - diluted (in shares)	10,792,290	10,287,562	10,694,351	10,247,779
Average number of potentially dilutive securities excluded from calculation (in shares)	237,545	631,392	283,894	722,538