Note 2 - Cash, Cash Equivalents, and Investments (Details Textual) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Corporate Debt Securities [Member]
Debt Securities, Held-to-maturity, Premium Paid on Purchase	$ 0	$ 0	$ 283,940	$ 221,156	$ 282,946