Treasury Stock (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended						5 Months Ended	12 Months Ended
	Aug. 31, 2011	Feb. 28, 2010	Feb. 28, 2009	Nov. 30, 2008	May 31, 2008	Feb. 28, 2008	May 31, 2008	May 31, 2011	May 31, 2008
Accelerated Share Repurchases Outstanding Common Stock									$ 200.0
Accelerated Share Repurchases, Initially Received Shares (in Shares)					5,100,000		5,100,000		5,100,000
Accelerated Share Repurchases, Additional Received Shares (in Shares)					700,000		700,000		700,000
Accelerated Share Repurchases, Shares Received Total (in Shares)					5,800,000		5,800,000		5,800,000
Accelerated Share Repurchases, Initial Price Paid Per Share (in Dollars per share)									$ 34.64
Stock Repurchase Program, Authorized Amount		20.0	5.0	10.0	20.0	20.0
Stock Repurchase Program Number Of Shares Repurchased (in Shares)					700,000		700,000	400,000	700,000
Stock Repurchase Program Repurchased Amount							20.0	9.7
Treasury Stock Acquired, Average Cost Per Share (in Dollars per share)							$ 30.09	$ 24.98
Common Shares Purchased (in Shares)								5,199,699
Common Shares Purchase Price Per Share (in Dollars per share)								$ 30.00
Purchase Of Common Stock Value Excluding Related Fees and Expenses								156.0
Purchase of Shares, Percentage of Common Shares Outstanding								15.10%
Fees Related To Shares Purchase								1.2
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 44.5