Long-Term Debt - Long-Term Debt Table (Details) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Long-term debt
Total long-term debt	$ 14,382,775	$ 14,513,284
Long-Term Debt, excluding subordinated debt
Long-term debt
Total long-term debt	14,382,775	14,513,284
Unsecured long-term debt
Long-term debt
Total long-term debt	6,927,110	6,847,334
Unsecured medium-term notes
Long-term debt
Long-term debt before unamortized discount	2,597,933	2,514,447
Unamortized discount	(416)	(418)
Total long-term debt	2,597,517	2,514,029
Medium-term notes sold through dealers
Long-term debt
Long-term debt before unamortized discount	2,261,861	2,228,459
Medium Term Notes Sold to Members
Long-term debt
Long-term debt before unamortized discount	336,072	285,988
Unsecured notes payable
Long-term debt
Long-term debt before unamortized discount	4,330,325	4,334,075
Unamortized discount	(732)	(770)
Total long-term debt	4,329,593	4,333,305
Secured long-term debt
Long-term debt
Total long-term debt	7,455,665	7,665,950
Collateral trust bonds
Long-term debt
Long-term debt before unamortized discount	6,257,711	6,257,711
Unamortized discount	(275,589)	(277,496)
Total long-term debt	5,982,122	5,980,215
Secured notes payable
Long-term debt
Total long-term debt	1,473,543	1,685,735
Guaranteed Underwriter Program Notes Payable
Long-term debt
Long-term debt before unamortized discount	4,295,250	4,299,000
Other Unsecured Notes Payable
Long-term debt
Long-term debt before unamortized discount	35,075	35,075
Federal Agricultural Mortgage Corporation Notes Payable
Long-term debt
Long-term debt before unamortized discount	1,455,313	1,667,505
Other Secured Notes Payable
Long-term debt
Long-term debt before unamortized discount	$ 18,230	$ 18,230