Goodwill and Other Intangibles (Details) - Schedule of other intangible assets subject to amortization Parenthetical (USD $) In Millions, unless otherwise specified	Feb. 28, 2015	May 31, 2014	Feb. 28, 2014
Customer Lists
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 3.9	$ 3.3	$ 3.0
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 14.5	$ 13.4	$ 13.1

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant