Debt, Derivatives and Hedging Activities (Details) (USD $)	3 Months Ended					0 Months Ended
	Aug. 31, 2013	Aug. 31, 2012	May 31, 2013	Aug. 31, 2013 Unsecured Debt [Member]	May 31, 2013 Unsecured Debt [Member]	Jun. 02, 2012 Notes Due 2012 [Member] Senior Notes [Member]	Jun. 05, 2012 Notes Due 2022 [Member] Senior Notes [Member]
Line of Credit Facility [Line Items]
Long-term debt, carrying amount				$ 1,309,000,000	$ 1,309,200,000
Long-term debt, fair value				1,399,200,000	1,447,100,000
Commercial paper program availability	300,000,000
Revolving credit facility, maximum borrowing capacity with accordion feature	450,000,000
Revolving credit facility amount outstanding	0		0
Repayments of Long-term Debt	167,000	225,154,000				225,000,000
Debt Instrument, Interest Rate, Stated Percentage						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
Foreign currency derivatives	$ (100,000)		$ 100,000