Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jan. 31, 2020	Jul. 31, 2019
Allowance for doubtful accounts	$ 0	$ 0
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,400	2,400
Preferred stock, shares issued
Treasury stock, shares	40	22
Class A common stock
Common stock, par value	$ 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	$ 0.01	$ 0.01
Common stock, shares authorized	40,000	40,000
Common stock, shares issued	9,980	9,876
Common stock, shares outstanding	9,940	9,854