Equity (Details) (USD $)	3 Months Ended				1 Months Ended
	Aug. 31, 2013	Aug. 31, 2012	Aug. 31, 2013 Patronage capital allocated	Aug. 31, 2012 Patronage capital allocated	May 31, 2013 CFC Cooperative educational fund Authorized Allocations	Jul. 31, 2013 CFC Patronage capital allocated Authorized Allocations	Jul. 31, 2013 CFC Members' capital reserve
Equity
Allocation of net earnings					$ 1,000,000	$ 81,000,000	$ 138,000,000
Retirement/allocation of net earnings authorized	$ (40,724,000)	$ (35,345,000)	$ (40,724,000)	$ (35,345,000)		$ 41,000,000
Retirement of allocated net earnings, percentage						0.50