Debt, Derivatives and Hedging Activities (Details) (USD $)	3 Months Ended		9 Months Ended					0 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	May 31, 2013	Feb. 28, 2014 Unsecured Debt	May 31, 2013 Unsecured Debt	Jun. 02, 2012 Notes Due 2012 Senior Notes	Jun. 05, 2012 Notes Due 2022 Senior Notes	Feb. 28, 2014 Current accrued liabilities	May 31, 2013 Accounts receivable, net
Line of Credit Facility [Line Items]
Long-term debt, carrying amount						$ 1,301,200,000	$ 1,309,200,000
Long-term debt, fair value						1,414,200,000	1,447,100,000
Commercial paper program availability	300,000,000		300,000,000
Revolving credit facility, maximum borrowing capacity with accordion feature	450,000,000		450,000,000
Revolving credit facility amount outstanding	0		0		0
Repayment of senior note debt			8,010,000	225,472,000				225,000,000
Senior notes, stated interest rate								6.00%	3.25%
Proceeds from issuance of long-term debt			0	250,000,000					250,000,000
Amortization of interest rate lock agreements	500,000	500,000	1,500,000	1,500,000
Foreign currency derivatives (less than $0.1 million as of May 31, 2013)										$ (400,000)	$ 100,000