Short-Term Debt and Credit Arrangements (Details) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2014		May 31, 2013
Short-Term Debt Outstanding
Short Term Debt	$ 4,785,334		$ 4,050,132
Total short-term debt	6,541,987		7,719,483
Long-term debt maturing within one year:
Total long-term debt maturing within one year	1,756,653		3,669,351
Commercial Paper Sold Through Dealers, Net Of Discounts
Short-Term Debt Outstanding
Short Term Debt	2,611,744	[1]	2,009,884	[1]
Commercial Paper Sold Directly To Mebers At Par
Short-Term Debt Outstanding
Short Term Debt	916,675	[1]	812,141	[1]
Commercial Paper Sold Directly To Nonmebers At Par
Short-Term Debt Outstanding
Short Term Debt	20,160	[1]	39,298	[1]
Select Notes
Short-Term Debt Outstanding
Short Term Debt	496,031		358,390
Bank Bid Notes
Short-Term Debt Outstanding
Short Term Debt	150,000		150,000
Daily Liquidity Fund Notes Sold DirectlyTomember
Short-Term Debt Outstanding
Short Term Debt	590,724		680,419
Medium Term Notes Sold Through Dealers
Long-term debt maturing within one year:
Total long-term debt maturing within one year	270,282		989,607
Medium Term Notes Sold to Members
Long-term debt maturing within one year:
Total long-term debt maturing within one year	365,845		391,318
Collateral Trust Bonds
Long-term debt maturing within one year:
Total long-term debt maturing within one year	854,605		1,504,949
Loan and Gurantees Subordinated Certificates
Long-term debt maturing within one year:
Total long-term debt maturing within one year	53,370		37,176
Member Capital Securities
Long-term debt maturing within one year:
Total long-term debt maturing within one year	181,480		0
Secured Notes Payable
Long-term debt maturing within one year:
Total long-term debt maturing within one year	27,174		742,402
Unsecured Notes Payable
Long-term debt maturing within one year:
Total long-term debt maturing within one year	$ 3,897		$ 3,899

[1] Backup liquidity is provided by our revolving credit agreements.