Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) - shares	Feb. 29, 2016	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)	179,368,804	178,117,334
Common stock, shares outstanding (shares)	107,064,235	111,702,949
Treasury stock, shares (shares)	72,304,569	66,414,385