Income Taxes (Components of Income Before Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
May 31, 2013	May 31, 2012	May 31, 2011
Income before income taxes consist of the following components:
U.S. operations	$ 485,046	$ 454,811	$ 377,922
Foreign operations	14,862	16,133	14,747
Income before income taxes	$ 499,908	$ 470,944	$ 392,669

The portion of earnings or loss from continuing operations before income taxes that is attributable to domestic operations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 1(i)

-Article 4

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- Definition

The portion of earnings or loss from continuing operations before income taxes that is attributable to foreign operations, which is defined as Income or Loss generated from operations located outside the entity's country of domicile.

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- Definition

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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