Note 2 - Change in Accounting Policy - Changes to Financial Statements (Details) - USD ($)	3 Months Ended						12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Balance (in shares)			12,226,306			13,115,341	12,226,306	13,115,341
Balance	$ 61,121,000	$ 60,986,000	$ 60,758,000	$ 61,949,000	$ 62,419,000	$ 61,751,000	$ 60,758,000	$ 61,751,000
Common stock repurchased and retired (in shares)							(951,010)	(910,700)
Common stock repurchased and retired	(1,049,000)	(1,097,000)	(833,000)	(1,116,000)	(960,000)	(756,000)	$ (4,002,000)	$ (3,882,000)
Common stock, $.01 par value: 50,000,000 shares authorized; 11,416,212 and 12,226,306 shares outstanding as of December 31, 2023 and December 31, 2022, respectively							114,000	123,000
Additional paid-in capital	16,552,000	16,865,000	17,190,000	17,402,000	17,700,000	17,951,000	$ 16,339,000	$ 17,099,000
Options exercised (in shares)							140,916	21,665
Options exercised	36,000	54,000	350,000	30,000	30,000		$ 464,000	$ 80,000
Retained earnings	46,205,000	45,468,000	45,026,000	45,157,000	45,408,000	45,360,000	46,552,000	45,025,000
Accumulated other comprehensive loss							(1,437,000)	(1,489,000)
Stock-based compensation expense	24,000	22,000	22,000	32,000	32,000	55,000	170,000	147,000
Total shareholders' equity	61,391,000	61,121,000	60,986,000	61,261,000	61,949,000	62,419,000	61,568,000	60,758,000
Total liabilities and shareholders' equity	64,611,000	64,341,000	64,055,000	65,081,000	66,694,000	66,747,000	68,763,000	64,803,000
Total comprehensive income (loss)							$ 4,241,000	$ 2,662,000
Balance (in shares)							11,416,212	12,226,306
Balance	61,391,000	61,121,000	60,986,000	61,261,000	61,949,000	62,419,000	$ 61,568,000	$ 60,758,000
Previously Reported [Member]
Balance	61,121,000	60,986,000	60,758,000	61,949,000	62,419,000	61,751,000	$ 60,758,000	61,751,000
Common stock repurchased and retired	(1,049,000)	(1,097,000)	(833,000)	(1,116,000)	(960,000)	(756,000)
Common stock, $.01 par value: 50,000,000 shares authorized; 11,416,212 and 12,226,306 shares outstanding as of December 31, 2023 and December 31, 2022, respectively								123,000
Additional paid-in capital	0	0	0	0	0	0		0
Options exercised	36,000	54,000	350,000	30,000	30,000
Retained earnings	62,757,000	62,333,000	62,216,000	62,559,000	63,108,000	63,311,000		62,124,000
Accumulated other comprehensive loss								(1,489,000)
Stock-based compensation expense	24,000	22,000	22,000	32,000	32,000	55,000
Total shareholders' equity	61,391,000	61,121,000	60,986,000	61,261,000	61,949,000	62,419,000		60,758,000
Total liabilities and shareholders' equity	64,611,000	64,341,000	64,055,000	65,081,000	66,694,000	66,747,000		64,803,000
Balance	61,391,000	61,121,000	60,986,000	61,261,000	61,949,000	62,419,000		60,758,000
Revision of Prior Period, Adjustment [Member]
Additional paid-in capital	16,552,000	16,865,000	17,190,000	17,402,000	17,700,000	17,951,000		17,099,000
Retained earnings	(16,552,000)	(16,865,000)	(17,190,000)	(17,402,000)	(17,700,000)	(17,951,000)		$ (17,099,000)
Total liabilities and shareholders' equity	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Common Stock [Member]
Balance (in shares)	11,875,556	12,135,556	12,226,306	12,728,173	12,945,341	13,115,341	12,226,306	13,115,341
Balance	$ 119,000	$ 122,000	$ 123,000	$ 128,000	$ 130,000	$ 132,000	$ 123,000	$ 132,000
Common stock repurchased and retired (in shares)	(249,110)	(275,000)	(200,000)	(259,200)	(225,500)	(170,000)	(951,010)	(910,700)
Common stock repurchased and retired	$ (2,000)	$ (3,000)	$ (2,000)	$ (2,000)	$ (2,000)	$ (2,000)	$ (10,000)	$ (9,000)
Options exercised (in shares)	10,000	15,000	109,250	8,332	8,332		140,916	21,665
Options exercised	$ 0	$ 0	$ 1,000	$ 0	$ 0			$ 0
Stock-based compensation expense	0	0	0	0	0	0		0
Total shareholders' equity	$ 117,000	$ 119,000	$ 122,000	$ 126,000	$ 128,000	$ 130,000	$ 114,000	123,000
Total comprehensive income (loss)								$ 0
Balance (in shares)	11,636,446	11,875,556	12,135,556	12,477,305	12,728,173	12,945,341	11,416,212	12,226,306
Balance	$ 117,000	$ 119,000	$ 122,000	$ 126,000	$ 128,000	$ 130,000	$ 114,000	$ 123,000
Common Stock [Member] | Previously Reported [Member]
Balance (in shares)	11,875,556	12,135,556	12,226,306	12,728,173	12,945,341	13,115,341	12,226,306	13,115,341
Balance	$ 119,000	$ 122,000	$ 123,000	$ 128,000	$ 130,000	$ 132,000	$ 123,000	$ 132,000
Common stock repurchased and retired (in shares)	(249,110)	(275,000)	(200,000)	(259,200)	(225,500)	(170,000)
Common stock repurchased and retired	$ (2,000)	$ (3,000)	$ (2,000)	$ (2,000)	$ (2,000)	$ (2,000)
Options exercised (in shares)	10,000	15,000	109,250	8,332	8,332
Options exercised	$ 0	$ 0	$ 1,000	$ 0	$ 0
Stock-based compensation expense	0	0	0	0	0	0
Total shareholders' equity	$ 117,000	$ 119,000	$ 122,000	$ 126,000	$ 128,000	$ 130,000		$ 123,000
Balance (in shares)	11,636,446	11,875,556	12,135,556	12,477,305	12,728,173	12,945,341		12,226,306
Balance	$ 117,000	$ 119,000	$ 122,000	$ 126,000	$ 128,000	$ 130,000		$ 123,000
Additional Paid-in Capital [Member]
Balance	16,865,000	17,190,000	17,099,000	17,700,000	17,951,000	18,131,000	17,099,000	18,131,000
Common stock repurchased and retired	(354,000)	(390,000)	(280,000)	(360,000)	(313,000)	(235,000)	(1,330,000)	(1,259,000)
Options exercised	36,000	54,000	349,000	30,000	30,000		463,000	80,000
Stock-based compensation expense	24,000	22,000	22,000	32,000	32,000	55,000	170,000	147,000
Total shareholders' equity	16,552,000	16,865,000	17,190,000	17,402,000	17,700,000	17,951,000	16,339,000	17,099,000
Total comprehensive income (loss)								0
Balance	16,552,000	16,865,000	17,190,000	17,402,000	17,700,000	17,951,000	16,339,000	17,099,000
Additional Paid-in Capital [Member] | Previously Reported [Member]
Balance	0	0	0	0	0	0	0	0
Common stock repurchased and retired	(41,000)	(65,000)	(371,000)	(62,000)	(62,000)	(55,000)		(227,000)
Options exercised	36,000	54,000	349,000	30,000	30,000
Stock-based compensation expense	24,000	22,000	22,000	32,000	32,000	55,000
Total shareholders' equity	0	0	0	0	0	0		0
Balance	0	0	0	0	0	0		0
Retained Earnings [Member]
Balance	45,468,000	45,026,000	45,025,000	45,408,000	45,360,000	44,357,000	45,025,000	44,357,000
Common stock repurchased and retired	(693,000)	(704,000)	(551,000)	(754,000)	(645,000)	(519,000)	(2,662,000)	(2,614,000)
Options exercised	0	0	0	0	0			0
Stock-based compensation expense	0	0	0	0	0	0	0	0
Total shareholders' equity	46,205,000	45,468,000	45,026,000	45,157,000	45,408,000	45,360,000	46,552,000	45,025,000
Total comprehensive income (loss)								3,282,000
Balance	46,205,000	45,468,000	45,026,000	45,157,000	45,408,000	45,360,000	46,552,000	45,025,000
Retained Earnings [Member] | Previously Reported [Member]
Balance	62,333,000	62,216,000	62,124,000	63,108,000	63,311,000	62,488,000	62,124,000	62,488,000
Common stock repurchased and retired	(1,006,000)	(1,029,000)	(460,000)	(1,052,000)	(896,000)	(699,000)		(3,646,000)
Options exercised	0	0	0	0	0
Stock-based compensation expense	0	0	0	0	0	0
Total shareholders' equity	62,757,000	62,333,000	62,216,000	62,559,000	63,108,000	63,311,000		62,124,000
Balance	62,757,000	62,333,000	62,216,000	62,559,000	63,108,000	63,311,000		62,124,000
AOCI Attributable to Parent [Member]
Balance	(1,331,000)	(1,352,000)	(1,489,000)	(1,287,000)	(1,022,000)	(869,000)	(1,489,000)	(869,000)
Common stock repurchased and retired	0	0	0	0	0	0		0
Options exercised	0	0	0	0	0		0	0
Stock-based compensation expense	0	0	0	0	0	0	0	0
Total shareholders' equity	(1,483,000)	(1,331,000)	(1,352,000)	(1,424,000)	(1,287,000)	(1,022,000)	(1,437,000)	(1,489,000)
Total comprehensive income (loss)								(620,000)
Balance	(1,483,000)	(1,331,000)	(1,352,000)	(1,424,000)	(1,287,000)	(1,022,000)	(1,437,000)	(1,489,000)
AOCI Attributable to Parent [Member] | Previously Reported [Member]
Balance	(1,331,000)	(1,352,000)	(1,489,000)	(1,287,000)	(1,022,000)	(869,000)	$ (1,489,000)	(869,000)
Common stock repurchased and retired	0	0	0	0	0	0
Options exercised	0	0	0	0	0
Stock-based compensation expense	0	0	0	0	0	0
Total shareholders' equity	(1,483,000)	(1,331,000)	(1,352,000)	(1,424,000)	(1,287,000)	(1,022,000)		(1,489,000)
Balance	$ (1,483,000)	$ (1,331,000)	$ (1,352,000)	$ (1,424,000)	$ (1,287,000)	$ (1,022,000)		$ (1,489,000)