Loans and Commitments (Details 12) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Pledging of Loans and Loans on Deposit
Cash	$ 1,025	$ 520
Collateral trust bonds 2007 indenture
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	6,091,704	6,149,139
Debt outstanding	5,397,711	5,397,711
Collateral trust bonds 1994 indenture
Pledging of Loans and Loans on Deposit
Debt outstanding	860,000	860,000
Notes payable \| Federal Agricultural Mortgage Corporation
Pledging of Loans and Loans on Deposit
Debt outstanding	1,455,313	1,667,505
Notes payable \| Federal Financing Bank
Pledging of Loans and Loans on Deposit
Debt outstanding	4,295,250	4,299,000
Clean Renewable Energy Bonds Series 2009A
Pledging of Loans and Loans on Deposit
Debt outstanding	18,230	18,230
Cash	605	520
Total pledged collateral	21,468	21,918
Mortgage notes \| Distribution system mortgage notes \| Collateral trust bonds 2007 indenture
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	5,931,485	5,987,767
Mortgage notes \| Distribution system mortgage notes \| Collateral trust bonds 1994 indenture
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	986,226	1,005,058
Mortgage notes \| Distribution and power supply system mortgage notes \| Federal Agricultural Mortgage Corporation
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	1,876,550	1,907,607
Mortgage notes \| Distribution and power supply system mortgage notes \| Clean Renewable Energy Bonds Series 2009A
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	20,863	21,398
RUS guaranteed loans qualifying as permitted investments \| Collateral trust bonds 2007 indenture
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	160,219	161,372
Mortgage notes receivable on deposit \| Distribution and power supply system mortgage notes \| Federal Financing Bank
Pledging of Loans and Loans on Deposit
Loans outstanding and pledged as collateral	$ 5,031,779	$ 5,076,428

Carrying amount as of the balance sheet date of assets that have been pledged as collateral.

No definition available.

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- Definition

Reflects the aggregate value of loans, trade receivables, securities and financial instruments that serve as collateral for obligations arising from a transfer of financial assets recorded as a secured borrowing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5086-111524

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)

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- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

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- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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