Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jul. 31, 2017	Jul. 31, 2016
Allowance for doubtful accounts	$ 2,657	$ 3,957
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized shares	10,000	10,000
Preferred stock, shares issued
Class A Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	35,000	35,000
Common stock, shares issued	3,272	3,272
Common stock, shares outstanding	1,574	1,574
Treasury stock, common stock shares	1,698	1,698
Class B Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	25,561	25,383
Common stock, shares outstanding	23,264	21,452
Treasury stock, common stock shares	2,297	3,931