Note 19 - Revisions of Previously Issued Unaudited Consolidated Financial Statements (Unaudited) - Balance Sheets (Details) - USD ($)	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Additional paid-in capital	$ 16,339,000	$ 16,552,000	$ 16,865,000	$ 17,190,000	$ 17,099,000	$ 17,402,000	$ 17,700,000	$ 17,951,000
Retained earnings	46,552,000	46,205,000	45,468,000	45,026,000	45,025,000	45,157,000	45,408,000	45,360,000
Total shareholders' equity	61,568,000	61,391,000	61,121,000	60,986,000	60,758,000	61,261,000	61,949,000	62,419,000	$ 61,751,000
Total liabilities and shareholders' equity	$ 68,763,000	64,611,000	64,341,000	64,055,000	64,803,000	65,081,000	66,694,000	66,747,000
Balance Sheet Amounts [Member]
Total shareholders' equity		61,391,000	61,121,000	60,986,000		61,261,000	61,949,000	62,419,000
Previously Reported [Member]
Additional paid-in capital		0	0	0	0	0	0	0
Retained earnings		62,757,000	62,333,000	62,216,000	62,124,000	62,559,000	63,108,000	63,311,000
Total shareholders' equity		61,391,000	61,121,000	60,986,000	60,758,000	61,261,000	61,949,000	62,419,000	$ 61,751,000
Total liabilities and shareholders' equity		64,611,000	64,341,000	64,055,000	64,803,000	65,081,000	66,694,000	66,747,000
Previously Reported [Member] | Balance Sheet Amounts [Member]
Total shareholders' equity		61,391,000	61,121,000	60,986,000		61,261,000	61,949,000	62,419,000
Revision of Prior Period, Adjustment [Member]
Additional paid-in capital		16,552,000	16,865,000	17,190,000	17,099,000	17,402,000	17,700,000	17,951,000
Retained earnings		(16,552,000)	(16,865,000)	(17,190,000)	$ (17,099,000)	(17,402,000)	(17,700,000)	(17,951,000)
Total liabilities and shareholders' equity		0	0	0		0	0	0
Revision of Prior Period, Adjustment [Member] | Balance Sheet Amounts [Member]
Total shareholders' equity		$ 0	$ 0	$ 0		$ 0	$ 0	$ 0