Income Taxes Valuation Allowances & Uncertain Tax Provisions (Details 6) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Changes in unrecognized tax benefits for all jurisdictions were as follows:
Gross unrecognized tax benefits	$ 476.9	$ 263.5
Prior year tax positions - increases	7.7	103.1
Current year tax positions	36.6	146.9
Prior year tax positions - decreases	(204.3)	(34.8)
Settlements	0	0
Effect of currency translation on unrecognized tax benefits	(0.1)	(1.8)
Gross unrecognized tax benefits	316.8	476.9	263.5
The amount of unrecognized tax benefits that, if recognized, would affect our effective tax rate in future periods	106.4
Accrued interest and penalties related to unrecognized tax benefits, which are reflected in other noncurrent liabilities	53.8	52.0
Gross decrease that impacts our effective tax rate due to the resolution of certain tax matters	179.3
Valuation Allowance [Abstract]
Net change in the deferred tax asset valuation allowance during the period	86.6	29.0	52.1
Foreign Country [Member]
Changes in unrecognized tax benefits for all jurisdictions were as follows:
Prior year tax positions - decreases	(187.7)
Reasonably possible gross unrecognized tax benefit decrease associated with non-U.S. subsidiaries	$ 30.0