Taxes (Details) - Schedule of effective income tax rate reconciliation (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed federal statutory provision	35.00%	35.00%	35.00%
State income tax provision, net of federal income tax benefit	3.60%	3.30%	4.30%
Difference in effective tax rates on earnings of foreign subsidiaries	3.70%	0.30%	0.20%
Charitable contributions	(1.10%)	(4.40%)	(0.70%)
Tax credits	(0.30%)	(0.40%)	(0.10%)
Valuation allowances	0.70%	2.40%	(1.40%)
Uncertain Positions	(27.10%)	0.00%	0.00%
Other - net	(2.40%)	(3.20%)	(1.00%)
Effective tax rates	12.10%	33.00%	36.30%
Total provision for income taxes	$ 6.1	$ 17.6	$ 61.6