CAPITAL STOCK AND STOCK-BASED AWARDS (Detail) - Schedule of Intrinsic value of stock options exercised, pretax stock-based compensation cost and related tax benefits (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Total intrinsic value of stock options exercised	$ 5.0	$ 0.4	$ 0.3
Stock-based compensation cost (pretax)	12.2	13.7	14.0
Tax benefits related to stock-based compensation cost	1.8	1.8	2.1
Weighted average grant date fair value per option	$ 9.30	$ 8.15	$ 8.34