Note 2 - Change in Accounting Policy (Details Textual) - 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	Dec. 31, 2021
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
Retained Earnings (Accumulated Deficit)	(46,205,000)	(45,468,000)	(45,026,000)	(45,157,000)	(45,408,000)	(45,360,000)	(46,552,000)	(45,025,000)
Equity, Attributable to Parent	61,391,000	61,121,000	60,986,000	61,261,000	61,949,000	62,419,000	61,568,000	60,758,000	$ 61,751,000
Stock Repurchased and Retired During Period, Value	1,049,000	1,097,000	833,000	1,116,000	960,000	756,000	4,002,000	3,882,000
Additional Paid-in Capital [Member]
Equity, Attributable to Parent	16,552,000	16,865,000	17,190,000	17,402,000	17,700,000	17,951,000	16,339,000	17,099,000	18,131,000
Stock Repurchased and Retired During Period, Value	354,000	390,000	280,000	360,000	313,000	235,000	1,330,000	1,259,000
Retained Earnings [Member]
Equity, Attributable to Parent	46,205,000	45,468,000	45,026,000	45,157,000	45,408,000	45,360,000	46,552,000	45,025,000	44,357,000
Stock Repurchased and Retired During Period, Value	693,000	704,000	551,000	754,000	645,000	519,000	$ 2,662,000	2,614,000
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 (Accumulated Deficit)	16,552,000	16,865,000	17,190,000	17,402,000	17,700,000	17,951,000		17,099,000
Previously Reported [Member]
Additional Paid in Capital	0	0	0	0	0	0		0
Retained Earnings (Accumulated Deficit)	(62,757,000)	(62,333,000)	(62,216,000)	(62,559,000)	(63,108,000)	(63,311,000)		(62,124,000)
Equity, Attributable to Parent	61,391,000	61,121,000	60,986,000	61,261,000	61,949,000	62,419,000		60,758,000	61,751,000
Stock Repurchased and Retired During Period, Value	1,049,000	1,097,000	833,000	1,116,000	960,000	756,000
Previously Reported [Member] | Additional Paid-in Capital [Member]
Equity, Attributable to Parent	0	0	0	0	0	0		0	0
Stock Repurchased and Retired During Period, Value	41,000	65,000	371,000	62,000	62,000	55,000		227,000
Previously Reported [Member] | Retained Earnings [Member]
Equity, Attributable to Parent	62,757,000	62,333,000	62,216,000	62,559,000	63,108,000	63,311,000		62,124,000	$ 62,488,000
Stock Repurchased and Retired During Period, Value	$ 1,006,000	$ 1,029,000	$ 460,000	$ 1,052,000	$ 896,000	$ 699,000		$ 3,646,000