Taxes (Details) - Schedule of effective income tax rate reconciliation (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Schedule of effective income tax rate reconciliation [Abstract]
Computed federal statutory provision	35.00%	35.00%	35.00%
State income tax provision, net of federal income tax benefit	3.30%	4.30%	5.20%
Difference in effective tax rates on earnings of foreign subsidiaries	0.30%	0.20%	(0.80%)
Charitable contributions	(4.40%)	(0.70%)	(1.50%)
Tax credits	(0.40%)	(0.10%)	(0.20%)
Valuation allowances	2.40%	(1.40%)	5.90%
Other - net	(3.20%)	(1.00%)	2.50%
Effective tax rates	33.00%	36.30%	46.10%
Total provision for income taxes (in Dollars)	$ 17.6	$ 61.6	$ 38.8