Goodwill and Intangible Assets - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
May 31, 2012	May 31, 2011	May 31, 2010
Goodwill [Line Items]
Amortization expense of acquired intangibles	$ 50.7	$ 41.7	$ 32.8
Customer-related
Goodwill [Line Items]
Intangible assets weighted average amorization periods	13.5	9.9
Contract-based
Goodwill [Line Items]
Intangible assets weighted average amorization periods	10.0	20.0

The calculated weighted-average amortization period of a major class of finite-lived intangible assets acquired during the current period either individually or as part of a group of assets (in either an asset acquisition or business combination). A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 44

-Subparagraph a(3)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6905858&loc=d3e16265-109275

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetWeightedAverageUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration