Employee Benefit Plans (Details) - Schedule of net periodic costs (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
Pension Plan, Defined Benefit [Member]
Employee Benefit Plans (Details) - Schedule of net periodic costs [Line Items]
Interest cost	$ 1.8	$ 1.7
Expected return on assets	(3.1)	(2.6)
Amortization of loss	0.4	0.5
Net periodic benefit (credit) cost	(0.9)	(0.4)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Employee Benefit Plans (Details) - Schedule of net periodic costs [Line Items]
Service cost	0	0
Interest cost	0.3	0.4
Net amortization of prior service credit	0	(0.1)
Amortization of loss	0.6	0.9
Net periodic benefit (credit) cost	$ 0.9	$ 1.2