Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) (USD $)	Aug. 31, 2012	May 31, 2012
Statement of Financial Position [Abstract]
Preferred stock, no par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	100,000	100,000
Preferred stock, shares outstanding ( in shares)	0	0
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	425,000,000	425,000,000
Common stock, shares issued (in shares)	174,357,822	173,745,913
Common stock, shares outstanding (in shares)	125,117,508	126,519,758
Treasury stock, shares (in shares)	49,240,314	47,226,155