Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Apr. 30, 2016	Jul. 31, 2015
Allowance for doubtful accounts	$ 4,027	$ 5,645
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	25,386	25,276
Common stock, shares outstanding	21,455	21,755
Treasury stock, common stock shares	3,931	3,521