Earnings Per Share (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		24 Months Ended			3 Months Ended	1 Months Ended
	Aug. 31, 2013	Aug. 31, 2012	Oct. 10, 2013	Jul. 30, 2013	Oct. 18, 2011	Aug. 31, 2013 Employee payroll taxes due on restricted stock [Member]	Oct. 10, 2013 Subsequent Event [Member]
Earnings Per Share, Basic and Diluted [Line Items]
Options granted excluded from the computation of diluted earnings per share (shares)	600,000	800,000
Additional amount authorized under share buyback program				500,000,000	500,000,000
Common stock purchased under a share buyback program (shares)	2,100,000		11,400,000			100,000	900,000
Aggregate purchase price of common stock under a share buyback program	$ 100.8		$ 484.6			$ 6.2	$ 46.3
Average price of common stock purchased under a share buyback program (dollars per share)			$ 42.44			$ 47.67