Comprehensive Income - Components of Comprehensive Income, Net of Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income including noncontrolling interests	$ 1,335,719	$ 1,061,028	$ 535,397
Pension and other postretirement, net of tax expense (benefit) of $(21,710), $17,776 and $(30,847) in 2012, 2011, and 2010, respectively	(38,216)	28,001	(47,667)
Unrealized net gain (loss) on available for sale investments, net of tax expense (benefit) of $199, 445 and $(447) in 2012, 2011 and 2010, respectively	355	716	(750)
Treasury locks and swaps, net of tax (benefit) expense of $449, $(2,180) and $227 in 2012, 2011 and 2010, respectively	586	(3,424)	356
Energy derivative instruments qualified for hedge accounting, net of tax expense (benefit) of $1,540 and $(1,540) in 2011 and 2010, respectively		2,419	(2,419)
Foreign currency translation adjustment, net of tax expense (benefit) of $(3,699), $2,842 and $(791) in 2012, 2011 and 2010, respectively	(5,855)	4,464	(1,242)
Other comprehensive income (loss)	(43,130)	32,176	(51,722)
Total comprehensive income	1,292,589	1,093,204	483,675
Comprehensive income attributable to noncontrolling interests	75,091	101,458	30,513
Comprehensive income attributable to CHS Inc.	1,217,498	991,746	453,162
Other Comprehensive Income (Loss), Tax [Abstract]
Pension and other postretirement, tax	(21,710)	17,776	(30,847)
Unrealized net gain (loss) on available for sale investments, tax	199	445	(447)
Treasury locks and swaps, tax	449	(2,180)	227
Energy derivative instruments qualified for hedge accounting, tax	0	1,540	(1,540)
Foreign currency translation adjustment, net of tax expense (benefit)	$ (3,699)	$ 2,842	$ (791)