Leases - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
May 31, 2014	May 31, 2013	May 31, 2012
Lease and Rental Expense [Line Items]
Rental expenses for all operating lease	$ 50.9	$ 46.5	$ 40.6

Amount of lease operating expense related to property used in oil and gas production.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 10

-Paragraph a

-Subparagraph 17

-Article 4

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