Goodwill and Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	May 31, 2012	May 31, 2011	May 31, 2010
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 724,687	$ 779,637	$ 569,090
Other intangible assets	525,484	538,566
Accumulated amortization	235,296	197,066
Other intangible assets, net	290,188	341,500
Customer-related
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	451,095	457,226
Accumulated amortization	214,285	181,372
Trademarks, finite life
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	7,996	8,659
Accumulated amortization	4,868	4,138
Contract-based
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	66,393	72,681
Accumulated amortization	$ 16,143	$ 11,556