Defined Contribution Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
May 31, 2013	May 31, 2012	May 31, 2011
401(k) [Member]
Defined Benefit Plan Disclosure [Line Items]
Required years of service for plan eligibility (years)	1 year
Total contributions to defined benefit plans	$ 28.4	$ 26.0	$ 21.1
Deferred Profit Sharing Plan (DPSP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions to defined benefit plans	1.4	1.3	1.0
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total contributions to defined benefit plans	$ 4.7	$ 5.7	$ 6.1

The increase in the fair value of plan assets from contributions made by the employer.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration