Note 3 - Summary of Significant Accounting Policies - Computation of Basic Net Income Per Share (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)	1,028,863	1,024,467	1,028,863	1,023,579
Common shares upon exercise of options and warrants (in shares)	2,764	10,176	3,785	10,176
Weighted average common shares outstanding, diluted (in shares)	1,031,627	1,034,643	1,032,648	1,033,755