Debt (Detail) - Schedule of debt (USD $) In Millions, unless otherwise specified	Feb. 29, 2012	May 31, 2011	Feb. 28, 2011
Debt, Long-term and Short-term, Combined Amount, Carrying Value	$ 165.3	$ 203.4	$ 220.1
Debt, Long-term and Short-term, Combined Amount, Fair Value	171.1	207.5	222.9
Less lines of credit, short-term debt and current portion of long-term debt	(12.6)	(43.5)	(49.5)
Less lines of credit, short-term debt and current portion of long-term debt	(12.6)	(43.5)	(49.5)
Total long-term debt	152.7	159.9	170.6
Total long-term debt	158.5	164.0	173.4
Term Loan [Member]
Debt, Long-term and Short-term, Combined Amount, Carrying Value		50.2	60.9
Debt, Long-term and Short-term, Combined Amount, Fair Value		50.2	60.9
Notes Due 2013 [Member]
Debt, Long-term and Short-term, Combined Amount, Carrying Value	152.7	152.5	152.5
Debt, Long-term and Short-term, Combined Amount, Fair Value	158.5	156.6	155.3
Line of Credit [Member]
Debt, Long-term and Short-term, Combined Amount, Carrying Value	12.6	0.7	6.7
Debt, Long-term and Short-term, Combined Amount, Fair Value	$ 12.6	$ 0.7	$ 6.7