Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Jun. 30, 2016	Sep. 30, 2015
Marketable securities, cost	$ 86,090,000	$ 87,123,000
Accounts receivable, allowance for doubtful accounts	$ 203,000	$ 357,000
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, shares authorized	300,000	300,000
Preferred stock, shares issued	0	0
Common Stock [Member]
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	8,048,132	8,028,882
Common stock, shares outstanding	8,048,132	8,028,882
Class B Stock [Member]
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	6,000,000	6,000,000
Common stock, shares issued	1,509,238	1,509,238
Common stock, shares outstanding	1,509,238	1,509,238