Reconciliation of Basic and Diluted Earnings Per Common Share (Parenthetical) (Detail) - $ / shares	May. 31, 2015	May. 31, 2014
2026 Senior Notes
Earnings Per Share Disclosure [Line Items]
Convertible notes average stock price, per share	$ 48.05	$ 48.05

The price per share of the conversion feature embedded in the debt instrument.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant