Employee Benefit Plans (Details) - Schedule of net periodic costs (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2013	Nov. 30, 2012
Other Pension Plan, Defined Benefit [Member]
Employee Benefit Plans (Details) - Schedule of net periodic costs [Line Items]
Interest cost	$ 1.8	$ 1.7	$ 3.6	$ 3.5
Expected return on assets	(3.2)	(2.6)	(6.3)	(5.3)
Amortization of loss	0.5	0.5	0.9	1.1
Net periodic benefit (credit) cost	(0.9)	(0.4)	(1.8)	(0.7)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Employee Benefit Plans (Details) - Schedule of net periodic costs [Line Items]
Service cost	0	0	0	0
Interest cost	0.3	0.4	0.7	0.8
Net amortization of prior service credit	0	(0.1)	(0.1)	(0.2)
Amortization of loss	0.6	0.9	1.2	1.9
Net periodic benefit (credit) cost	$ 0.9	$ 1.2	$ 1.8	$ 2.5