Condensed Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Allowance for credit losses	$ 523	$ 510
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury shares (in shares)	1,137,995	1,137,995
Common Stock, Excluding Class B Convertible Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.1	$ 0.1
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares outstanding (in shares)	12,256,197	12,215,668
Class B Convertible Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.1	$ 0.1
Common stock, shares authorized (in shares)	3,000,000	3,000,000
Common stock, shares outstanding (in shares)	1,022,887	1,022,887