Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	May 31, 2013	Aug. 31, 2012
Allowance for doubtful accounts	$ 10,857	$ 9,480
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	129,060,664	129,060,664
Common stock, shares outstanding	116,899,574	116,351,424
Treasury stock, shares	12,161,090	12,709,240