Earnings Per Share (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended	9 Months Ended	1 Months Ended	30 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	Jul. 30, 2013	Oct. 18, 2011	Feb. 28, 2014 Employee payroll taxes due on restricted stock	Feb. 28, 2014 Employee payroll taxes due on restricted stock	Apr. 09, 2014 Subsequent Event	Apr. 09, 2014 Subsequent Event
Earnings Per Share, Basic and Diluted [Line Items]
Options granted and excluded from the computation of diluted earnings per share (shares)	400,000	600,000	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)	0		3,200,000					100,000	0	11,600,000
Aggregate purchase price of common stock under a share buyback program			$ 157.7				$ 0.2	$ 6.7		$ 495.3
Average price of common stock purchased under a share buyback program (dollars per share)								$ 48.20		$ 42.58