Earnings Per Share (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended				3 Months Ended	6 Months Ended	1 Months Ended	27 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2013	Nov. 30, 2012	Jul. 30, 2013	Oct. 18, 2011	Nov. 30, 2013 Employee payroll taxes due on restricted stock	Nov. 30, 2013 Employee payroll taxes due on restricted stock	Jan. 09, 2014 Subsequent Event	Jan. 09, 2014 Subsequent Event
Earnings Per Share, Basic and Diluted [Line Items]
Options granted excluded from the computation of diluted earnings per share (shares)	500,000	400,000	700,000	700,000
Additional amount authorized under share buyback program					500,000,000	500,000,000
Common stock purchased under a share buyback program (shares)	1,100,000		3,200,000					100,000	0	11,600,000
Aggregate purchase price of common stock under a share buyback program	$ 56.9		$ 157.7				$ 0.3	$ 6.5		$ 495.3
Average price of common stock purchased under a share buyback program (dollars per share)								$ 47.89		$ 42.58