Long-Term Debt and Derivatives (Narrative) (Details) (USD $)	12 Months Ended								0 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011	May 31, 2013 Other comprehensive Income [Member]	May 31, 2012 Other comprehensive Income [Member]	May 31, 2011 Other comprehensive Income [Member]	May 31, 2013 Notes Due Through 2036 [Member] Unsecured Debt [Member]	May 31, 2012 Notes Due Through 2036 [Member] Unsecured Debt [Member]	Jun. 02, 2012 Notes Due 2012 [Member] Senior Notes [Member]	Jun. 05, 2012 Notes Due 2022 [Member] Senior Notes [Member]	May 31, 2013 Forward Contracts [Member]	May 31, 2012 Forward Contracts [Member]
Debt Instrument [Line Items]
Long-term debt, carrying amount							$ 1,309,166,000	$ 1,284,802,000
Long-term debt, fair value							1,447,100,000	1,420,200,000
Letters of credit outstanding, amount	85,800,000	85,700,000
Interest paid	68,400,000	62,300,000	49,200,000
Commercial paper program availability	300,000,000
Revolving credit facility, maximum borrowing capacity with accordion feature	450,000,000
Debt to EBITDA ratio covenant requirement	3.5
Payments on long term debt	225,636,000	1,323,000	502,208,000						225,000,000
Stated interest rate percentage on long term debt (percent)									6.00%	3.25%
Net proceeds from issuance of long-term debt										25,000,000
Proceeds from issuance of debt	250,000,000	0	1,002,281,000							250,000,000
Amortization of interest rate lock agreements				2,000,000	1,500,000	800,000
Interest rate derivatives, less than $0.1 million in 2013											100,000	0
Loss on foreign currency exchange hedges, less than $0.1 million in 2012	0	100,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Maturities of long term debt, next twelve months	8,200,000
Maturities of long term debt, year two	500,000
Maturities of long term debt, year three	200,000
Maturities of long term debt, year four	250,200,000
Maturities of long term debt, year five	$ 300,100,000