Employee Benefit Plans (Details) - Schedule of net periodic costs (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013
Components of net periodic benefit (credit) cost:
Amortization of (gain) loss			$ 4.9	$ 2.1
Other Pension Plan, Defined Benefit
Components of net periodic benefit (credit) cost:
Service cost	0	0	0	0
Interest cost	1.6	1.8	3.4	3.6
Expected return on assets	(2.2)	(3.2)	(4.7)	(6.3)
Net amortization of prior service credit	0	0	0	0
Benefit cost of settlement event	3.7	0	3.7	0
Amortization of (gain) loss	0.4	0.5	0.7	0.9
Net periodic benefit (credit) cost	3.5	(0.9)	3.1	(1.8)
Other Postretirement Benefit Plan, Defined Benefit
Components of net periodic benefit (credit) cost:
Service cost	0	0	0	0
Interest cost	0.3	0.3	0.6	0.7
Expected return on assets	0	0	0	0
Net amortization of prior service credit	0	0	(0.1)	(0.1)
Benefit cost of settlement event	0	0	0	0
Amortization of (gain) loss	0.3	0.6	0.7	1.2
Net periodic benefit (credit) cost	$ 0.6	$ 0.9	$ 1.2	$ 1.8