Derivative Instruments and Hedging Activities - Schedule of Interest Rate Swap (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Aug. 31, 2014	Aug. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amount of gain (loss) recognized in OCI	$ 5.3	$ 21.7
Amount of (gain) loss reclassified from accumulated OCI into interest expense (effective portion)	4.8	7.5
Amount (gain) loss recognized in other income (expense) (ineffective portion and amount excluded from effectiveness testing)	$ 0	$ 0

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1),(2)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration