Earnings per Share (Summary of Share Buyback Program) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
May 31, 2014	May 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchased under a share buyback program (shares)	6,665	5,075
Average price of common stock purchased under a share buyback program (dollars per share)	$ 54.31	$ 40.97
Aggregate purchase price of common stock under a share buyback program	$ 361,960	$ 207,932
October 18, 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchased under a share buyback program (shares)	3,324	5,075
Average price of common stock purchased under a share buyback program (dollars per share)	$ 48.87	$ 40.97
Aggregate purchase price of common stock under a share buyback program	162,460	207,932
July 30, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchased under a share buyback program (shares)	3,341	0
Average price of common stock purchased under a share buyback program (dollars per share)	$ 59.72	$ 0.00
Aggregate purchase price of common stock under a share buyback program	$ 199,500	$ 0

Represents the average price of common stock that has been repurchased during the period under share repurchase program.

No definition available.

+ Details

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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- Definition

Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

+ Details

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