Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares shares in Millions	Aug. 31, 2015	May. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	600.0	600.0
Common stock, shares issued	360.5	361.2
Common stock, shares outstanding	360.5	361.2