Debt, Derivatives and Hedging Activities (Details) (USD $)	3 Months Ended
Aug. 31, 2014	Aug. 31, 2013	May 31, 2014
Line of Credit Facility [Line Items]
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
Amortization of interest rate lock agreements	500,000	500,000
Level 2 \| Foreign Exchange Forward \| Fair Value, Measurements, Recurring
Line of Credit Facility [Line Items]
Current accrued liabilities	265,000		286,000
Unsecured Debt
Line of Credit Facility [Line Items]
Long-term debt, carrying amount	1,300,000,000		1,301,000,000
Long-term debt, fair value	$ 1,425,900,000		$ 1,421,000,000

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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