Employee Benefit Plans (Details) - Schedule of net periodic costs (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Components of net periodic benefit (credit) cost:
Amortization of (gain) loss			$ 6.2	$ 2.9
Other Pension Plan, Defined Benefit
Components of net periodic benefit (credit) cost:
Service cost	0	0	0	0
Interest cost	1.7	1.8	5.0	5.4
Expected return on assets	(2.3)	(3.2)	(7.0)	(9.5)
Net amortization of prior service credit	0	0	0	0
Benefit cost of settlement event	0.6	0	4.3	0
Amortization of (gain) loss	0.4	0.5	1.1	1.4
Net periodic benefit (credit) cost	0.4	(0.9)	3.4	(2.7)
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	1.0	1.0
Expected return on assets	0	0	0	0
Net amortization of prior service credit	(0.1)	(0.1)	(0.2)	(0.2)
Benefit cost of settlement event	0	0	0	0
Amortization of (gain) loss	0.4	0.5	1.0	1.7
Net periodic benefit (credit) cost	$ 0.6	$ 0.7	$ 1.8	$ 2.5