Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Feb. 28, 2014	May 31, 2014	May 31, 2013	May 31, 2012	May 31, 2011
Income Tax And Non Income Tax Disclosure [Abstract]
Unrecognized tax settlement	$ 13.8
Undistributed earnings of foreign subsidiaries indefinitely reinvested		73.6
Deferred income tax liabilities on undistributed foreign earnings		2.0
Net deferred tax assets		85.1	94.1
Current deferred income taxes		81.0	79.2
Noncurrent deferred income taxes		4.1	14.9
Decrease in deferred tax valuation allowance		1.9	2.5
Foreign operating loss carryforwards		109.6
Unrecognized tax benefits		14.4	35.5	38.7	30.8
Income tax penalties and interest accrued		1.1	6.5	7.1
Unrecognized tax benefits that would impact effective tax rate		11.7	21.8	18.1
Tax benefit from income tax penalties and interest expense		5.3	0.5	(2.4)
Period increase (decrease) in unrecognized tax benefits		$ (21.1)	$ (3.2)