Note 9 - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Basic and diluted earnings per share calculation:
Net income to common stockholders						$ 306,893	$ 805,265
Weighted average number of common shares outstanding - basic (in shares)						4,486,788	4,491,135
Basic net income per share (in dollars per share)	$ 0.01	$ 0.02	$ 0	$ 0.02	$ 0.02	$ 0.07	$ 0.18
Weighted average number of common shares outstanding - diluted (in shares)						4,497,599	4,500,027
Diluted net income per share (in dollars per share)	$ 0.01	$ 0.02	$ 0	$ 0.02	$ 0.02	$ 0.07	$ 0.18