Equities Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 7,905,825
Reversal of prior year patronage and redemption estimates			4,270
Patronage Refunds			0
Redemptions of equities			(4,269)
Preferred stock dividends			(126,501)
Other, net			(2,139)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 229,146	$ (46,140)	575,391	$ 177,775
Net income (loss) attributable to CHS Inc.	229,333	(45,185)	576,090	178,532
Net income (loss) attributable to noncontrolling interests	(187)	(955)	(699)	(757)
Other comprehensive income (loss), net of tax	(1,501)	1,742	13,944	2,026
Estimated 2018 cash patronage refunds			(119,747)
Estimated 2018 equity redemptions			(84,241)
Ending Balance	8,162,533		8,162,533
Capital equity certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			3,906,426
Reversal of prior year patronage and redemption estimates			4,270
Patronage Refunds			0
Redemptions of equities			(3,814)
Other, net			(5,999)
Estimated 2018 equity redemptions			(84,241)
Ending Balance	3,816,642		3,816,642
Nonpatronage Equity Certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			29,836
Reversal of prior year patronage and redemption estimates			0
Patronage Refunds			0
Redemptions of equities			(86)
Other, net			(113)
Ending Balance	29,637		29,637
Non-qualified Equity Certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			405,387
Reversal of prior year patronage and redemption estimates			(126,333)
Patronage Refunds			128,831
Redemptions of equities			(369)
Other, net			(381)
Ending Balance	407,135		407,135
Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			2,264,038
Patronage Refunds			0
Redemptions of equities			0
Ending Balance	2,264,038		2,264,038
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(183,670)	(211,726)
Patronage Refunds			0
Other comprehensive income (loss), net of tax			13,944	2,026
Ending Balance	(169,726)	$ (209,700)	(169,726)	$ (209,700)
Capital Reserves [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			1,471,217
Reversal of prior year patronage and redemption estimates			126,333
Patronage Refunds			(128,831)
Preferred stock dividends			(126,501)
Other, net			4,517
Net income (loss) attributable to CHS Inc.			576,090
Estimated 2018 cash patronage refunds			(119,747)
Ending Balance	1,803,078		1,803,078
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			12,591
Patronage Refunds			0
Other, net			(163)
Net income (loss) attributable to noncontrolling interests			(699)
Ending Balance	$ 11,729		$ 11,729