Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	May 31, 2011	May 31, 2010
Consolidated Balance Sheets
Allowance on accounts receivable (in dollars)	$ 17,057	$ 14,297
Preferred stock, shares authorized	100,000	100,000
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	425,000,000	425,000,000
Common stock, shares issued	173,346,180	173,207,493
Common stock, shares outstanding	137,583,884	152,869,848
Treasury stock, shares	35,762,296	20,337,645