Income Tax - Change in Valuation Allowance (Details) (USD $) In Thousands, unless otherwise specified				12 Months Ended
May 31, 2014	May 31, 2013	May 31, 2012	May 31, 2014 Valuation Allowance, Capital Loss Carryforward [Member]	May 31, 2014 Valuation Allowance, Other Tax Carryforward [Member]	May 31, 2013 Valuation Allowance, Other Tax Carryforward [Member]	May 31, 2014 Foreign Tax Authority [Member] Valuation Allowance, Operating Loss Carryforwards [Member]	May 31, 2013 Foreign Tax Authority [Member] Valuation Allowance, Operating Loss Carryforwards [Member]	May 31, 2013 Foreign Tax Authority [Member] Valuation Allowance, Tax Credit Carryforward [Member]
Movement in Deferred Tax Valuation Allowance [Roll Forward]
Valuation allowance, beginning of period	$ (7,199)	$ (28,464)	$ (26,090)
Valuation allowance, change				18,061	382	1,026	2,822	(3,415)	15
Valuation allowance, end of period	$ (7,199)	$ (28,464)	$ (26,090)

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

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