Derivative Financial Instruments (Details Textual) (Interest rate swaps, USD $)	Feb. 28, 2014	May 31, 2013
Derivative [Line Items]
Notional amount	$ 8,296,809,000	$ 8,788,329,000
Assets Needed to be Posted as Collateral for Immediate Settlement Aggregate Fair Value	9,000,000
Derivative, Net Liability Position, Aggregate Fair Value	167,000,000
Specific Counterparty
Derivative [Line Items]
Notional amount	$ 450,000,000

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

The aggregate fair value of assets needed to be posted as collateral on deposit and immediately settle the derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

No definition available.

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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959

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