Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) (USD $)	Aug. 31, 2013	May 31, 2013
Statement of Financial Position [Abstract]
Preferred stock, no par value (dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (shares)	100,000	100,000
Preferred stock, shares outstanding (shares)	0	0
Common stock, no par value (dollars per share)	$ 0	$ 0
Common stock, shares authorized (shares)	425,000,000	425,000,000
Common stock, shares issued (shares)	175,492,504	174,786,010
Common stock, shares outstanding (shares)	120,778,629	122,281,507
Treasury stock, shares (shares)	54,713,875	52,504,503