Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Feb. 28, 2015	Feb. 28, 2015
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, period increase (decrease)	$ 0.4	$ 1.4
Unrecognized tax benefits, increase in accrued interest (less than $0.1 million for the three months ended February 28, 2015)	$ 0.1	$ 0.2

The net amount of all increases and decreases in unrecognized tax benefits for the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15A

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

Name:	us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration