Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2023	Sep. 30, 2022
Marketable securities, cost	$ 85,514,000	$ 94,879,000
Accounts receivable, allowance for doubtful accounts	$ 545,000	$ 370,000
Preferred stock, par value	$ 10	$ 10
Preferred stock, shares authorized	300,000	300,000
Preferred stock, shares issued	0	0
Common Stock [Member]
Common stock, par value	$ 10	$ 10
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	12,338,845	12,338,845
Common stock, shares outstanding	12,338,845	12,338,845
Class B Stock [Member]
Common stock, par value	$ 10	$ 10
Common stock, shares authorized	6,000,000	6,000,000
Common stock, shares issued	2,318,857	2,318,857
Common stock, shares outstanding	2,318,857	2,318,857