Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data	May 31, 2011	Aug. 31, 2010
Current assets:
Allowance for collection losses	$ 25,964	$ 29,721
Stockholders' equity:
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	115,435,601	114,325,349
Treasury stock, shares	13,625,063	14,735,315