Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
May. 31, 2015	May. 31, 2014	May. 31, 2013
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in dollars per share)	$ 1.08	$ 0.93	$ 0.81

Aggregate dividends declared during the period for each share of common stock outstanding.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration