Severance and Exit Costs (Detail) - Schedule of accrued severance cost associated with cost reduction measures (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	May 31, 2012
Beginning balance	$ 2.7	$ 1.9	$ 1.9
Accruals	1.3	3.3	14.9
Payments	(2.9)	(2.8)	(14.1)
Ending balance	$ 1.1	$ 2.4	$ 2.7