Equities Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 7,905,825
Reversal of prior year redemption estimates			2,621
Patronage Refunds			0
Redemptions of equities			(2,621)
Preferred stock dividends			(126,501)
Other, net			101
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 166,626	$ 14,973	346,245	$ 223,915
Net income (loss) attributable to CHS Inc.	166,674	14,567	346,757	223,717
Net income (loss) attributable to noncontrolling interests	(48)	406	(512)	198
Other comprehensive income (loss), net of tax	10,219	14,778	15,445	284
Estimated 2018 cash patronage refunds			(46,879)
Estimated 2018 equity redemptions			(32,276)
Ending Balance	8,061,960		8,061,960
Capital equity certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			3,906,426
Reversal of prior year redemption estimates			2,621
Patronage Refunds			0
Redemptions of equities			(2,402)
Other, net			(4,150)
Estimated 2018 equity redemptions			(32,276)
Ending Balance	3,870,219		3,870,219
Nonpatronage Equity Certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			29,836
Reversal of prior year redemption estimates			0
Patronage Refunds			0
Redemptions of equities			(69)
Other, net			(111)
Ending Balance	29,656		29,656
Non-qualified Equity Certificates [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			405,387
Reversal of prior year redemption estimates			(126,333)
Patronage Refunds			128,858
Redemptions of equities			(150)
Other, net			(345)
Ending Balance	407,417		407,417
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			15,445	284
Ending Balance	(168,225)	$ (211,442)	(168,225)	$ (211,442)
Capital Reserves [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			1,471,217
Reversal of prior year redemption estimates			126,333
Patronage Refunds			(128,858)
Preferred stock dividends			(126,501)
Other, net			4,768
Net income (loss) attributable to CHS Inc.			346,757
Estimated 2018 cash patronage refunds			(46,879)
Ending Balance	1,646,837		1,646,837
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			12,591
Patronage Refunds			0
Other, net			(61)
Net income (loss) attributable to noncontrolling interests			(512)
Ending Balance	$ 12,018		$ 12,018