Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Thousands, $ in Thousands	Apr. 30, 2021	Jul. 31, 2020
Allowance for doubtful accounts (in Dollars)	$ 0	$ 0
Preferred stock par value (in Dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,400	2,400
Preferred stock, shares issued
Treasury stock, shares	58	40
Class A common stock
Common stock, par value (in Dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	2,600	2,600
Common stock, shares issued	525	525
Common stock, shares outstanding	525	525
Class B common stock
Common stock, par value (in Dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	40,000	40,000
Common stock, shares issued	13,683	13,625
Common stock, shares outstanding	11,788	11,749