Employee Benefit Plans (Detail) - Schedule Of Net Benefit Costs (USD $) In Millions	3 Months Ended
	Aug. 31, 2011	Aug. 31, 2010
Pension Plans, Defined Benefit [Member]
Service cost		$ 0.1
Interest cost	2.1	2.2
Expected return on assets	(2.7)	(2.4)
Amortization of loss	0.3	0.5
Net periodic benefit costs	(0.3)	0.4
Other Postretirement Benefit Plans, Defined Benefit [Member]
Service cost	0
Interest cost	0.5	0.5
Net amortization of prior service credit	(0.2)	(0.2)
Amortization of loss	1.0	0.5
Net periodic benefit costs	$ 1.3	$ 0.8