Note 1 - Nature of Operations and Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net income available to common shareholders									$ 10,638,142	$ 6,832,214	$ 9,415,090
Weighted average common shares outstanding (in shares)									4,344,348	4,330,525	4,405,575
Effect of dilutive securities (in shares)									21,684	19,499	57,984
Weighted average diluted shares outstanding (in shares)									4,366,032	4,350,024	4,463,559
Basic income per common share (in dollars per share)	$ 0.58	$ 0.78	$ 0.58	$ 0.51	$ 0.22	$ 0.44	$ 0.43	$ 0.49	$ 2.45	$ 1.58	$ 2.14
Diluted income per common share (in dollars per share)	$ 0.57	$ 0.78	$ 0.58	$ 0.51	$ 0.22	$ 0.43	$ 0.43	$ 0.49	$ 2.44	$ 1.57	$ 2.11