Employee Benefit Plans (Details) - Schedule of net periodic costs - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Components of net periodic benefit (credit) cost:
Amortization of (gain) loss	$ 1.0	$ 0.7
Pension Plans
Components of net periodic benefit (credit) cost:
Service cost	0.0	0.0
Interest cost	1.5	1.7
Expected return on assets	(1.9)	(2.5)
Net amortization of prior service credit	0.0	0.0
Amortization of (gain) loss	0.4	0.3
Net periodic benefit (credit) cost	0.0	(0.5)
Post-Retirement Benefits
Components of net periodic benefit (credit) cost:
Service cost	0.0	0.0
Interest cost	$ 0.3	0.3
Expected return on assets		0.0
Net amortization of prior service credit	$ 0.0	0.0
Amortization of (gain) loss	0.6	0.4
Net periodic benefit (credit) cost	$ 0.9	$ 0.7