Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Apr. 30, 2013	Jul. 31, 2012
Allowance for doubtful accounts	$ 13,428	$ 13,055
Preferred stock, par value (In dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized shares	10,000	10,000
Preferred stock, shares issued
Class A common stock
Common stock, par value (In dollars per share)	$ 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 (In dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	24,151	24,112
Common stock, shares outstanding	21,273	21,342
Treasury stock, common stock shares	2,878	2,770