Consolidated Balance Sheets (Parenthetical) - USD ($)	May 31, 2017	May 31, 2016
Balance Sheets [Abstract]
Allowance for doubtful accounts related to accounts receivable	$ 185,000	$ 185,000
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	12,500,000	12,500,000
Common stock, shares issued	3,114,163	3,114,163
Common stock, shares outstanding	1,962,062	1,962,062
Treasury stock, shares	1,152,101	1,152,101