Equities Changes in Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2013	May 31, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent			$ 4,455,341	$ 3,915,592
Net Income (Loss) Attributable to Parent	250,796	405,062	869,589	899,740
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent			5,852	(7,477)
Retirements Of Equities			(184,955)	(138,421)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock			(18,408)	(18,408)
Change in Accrued Dividends and Equities Payable			347,491	(361,391)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests				(96,720)
Stockholders' Equity, Other			3,917	454
Stockholders' Equity Attributable to Parent	4,984,966	4,361,151	4,984,966	4,361,151
Stockholders' Equity Attributable to Noncontrolling Interest			17,982
Net income attributable to noncontrolling interests	1,533	1,656	4,139	75,095
Stockholders' Equity Attributable to Noncontrolling Interest	21,887	16,175	21,887	16,175
Patronage Refunds [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Patronage Refunds			(975,998)	(676,143)
Dividends and equity retirement determination			969,862	674,678
Capital equity certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends and equity retirement determination			184,955	136,000
Equity Certificates Issued During Period, Value, New Issues			18,211	29,156
Capital Reserves [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends and equity retirement determination			4,091	4,091
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests				(337,145)
Stockholders' Equity, Other			1,001	472
Stockholders' Equity Attributable to Noncontrolling Interest				349,728
Payments of Ordinary Dividends, Noncontrolling Interest			1,235	77,519
Distributions accrued for noncontrolling interests				$ (5,544)