Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) - shares	Aug. 31, 2015	May. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, shares authorized (shares)	100,000	100,000
Preferred stock, shares outstanding (shares)	0	0
Common stock, shares authorized (shares)	425,000,000	425,000,000
Common stock, shares issued (shares)	179,023,676	178,117,334
Common stock, shares outstanding (shares)	110,021,667	111,702,949
Treasury stock, shares (shares)	69,002,009	66,414,385