Restatement of Previously Issued Consolidated Financial Statements - Summary of Impacts of the Restatement Adjustments on Previously Reported Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	Aug. 31, 2015
Current assets:
Cash and cash equivalents	$ 450,617	$ 533,887	$ 219,273	$ 249,767	$ 181,379	$ 266,748	$ 276,137	$ 516,646	$ 290,273	$ 967,717
Receivables	2,460,401	2,248,213	1,836,490	2,058,222	1,892,168	2,767,967	2,767,150	3,034,083
Inventories	2,768,649	2,913,507	3,676,325	3,111,963	2,601,604	2,688,949	3,730,682	3,143,551
Derivative assets	329,757	250,005	251,048	166,557	218,742	206,187	233,429	277,498
Margin and related deposits	151,150	253,141	188,167	206,955	206,062	251,695	290,291	312,899
Supplier advance payments	288,423	426,607	658,815	542,770	249,234	431,433	701,705	476,907
Other current assets	244,208	190,680	296,982	270,674	281,925	265,469	196,237	187,524
Total current assets	6,693,205	6,816,040	7,127,100	6,606,908	5,631,114	6,878,448	8,195,631	7,949,108
Investments	3,711,925	3,787,163	3,752,876	3,777,000	3,750,993	3,841,749	3,802,379	3,828,899
Property, plant and equipment	5,141,719	5,140,106	5,179,868	5,266,408	5,356,434	5,405,651	5,404,347	5,443,079
Other assets	834,329	960,240	943,552	997,402	1,080,381	955,532	1,056,873	1,054,454
Total assets	16,381,178	16,703,549	17,003,396	16,647,718	15,818,922	17,081,380	18,459,230	18,275,540
Current liabilities:
Notes payable	2,272,196	2,868,506	3,071,639	2,480,264	1,985,163	3,321,808	3,867,438	3,227,564
Current portion of long-term debt	167,565	53,056	46,290	71,022	156,345	193,096	205,136	206,894
Customer margin deposits and credit balances	137,395	137,999	106,323	139,868	157,914	132,479	149,625	180,850
Customer advance payments	409,088	372,590	756,642	413,519	423,770	391,122	897,464	543,411
Accounts payable	1,844,489	1,898,172	1,853,974	2,444,650	1,991,294	1,865,803	1,919,421	2,574,006
Derivative liabilities	438,465	316,831	361,909	207,426	300,946	233,955	232,507	282,658
Accrued expenses	511,032	538,249	465,032	425,912	454,996	436,111	392,058	397,446
Dividends and equities payable	153,941	209,718	128,700	121,209	12,121	134,718	131,380	239,857	162,439
Total current liabilities	5,934,171	6,395,121	6,790,509	6,303,870	5,482,549	6,709,092	7,795,029	7,652,686
Long-term debt	1,762,690	1,905,515	1,915,843	1,936,744	2,023,448	2,046,264	2,051,567	1,958,907
Long-term deferred tax liabilities	182,770	203,208	165,659	348,902	329,980	369,170	531,522	511,821
Other liabilities	336,519	278,869	265,028	315,254	277,305	276,483	272,532	332,610
Commitments and contingencies (Note 15)
Equities:
Preferred stock	2,264,038	2,264,038	2,264,038	2,264,038	2,264,038	2,264,063	2,244,114	2,244,132
Equity certificates	4,609,456	4,253,414	4,307,292	4,319,840	4,341,649	4,214,657	4,201,803	4,194,534
Accumulated other comprehensive loss	(199,915)	(167,302)	(167,230)	(177,341)	(180,360)	(208,568)	(211,091)	(224,935)
Capital reserves	1,482,003	1,559,040	1,450,326	1,324,372	1,267,808	1,397,834	1,560,498	1,592,434		1,485,433
Total CHS Inc. equities	8,155,582	7,909,190	7,854,426	7,730,909	7,693,135	7,667,986	7,795,324	7,806,165
Noncontrolling interests	9,446	11,646	11,931	12,039	12,505	12,385	13,256	13,351
Total equities	8,165,028	7,920,836	7,866,357	7,742,948	7,705,640	7,680,371	7,808,580	7,819,516	7,759,159	7,551,439
Total liabilities and equities	16,381,178	16,703,549	17,003,396	16,647,718	15,818,922	17,081,380	18,459,230	18,275,540
Long-term derivative assets	23,084				40,897
Goodwill	$ 138,464				138,454				144,284
As Previously Reported
Current assets:
Cash and cash equivalents		533,887	190,426	252,129	181,379	267,229	249,801	515,484	279,313	953,813
Receivables		2,198,211	1,765,640	2,059,623	1,869,632	2,722,325	2,697,699	3,052,989
Inventories		2,940,907	3,650,158	3,046,101	2,576,585	2,684,087	3,752,218	3,117,935
Derivative assets		483,794	429,625	283,256	232,017	388,188	386,613	419,103
Margin and related deposits		253,141	188,167	206,955	206,062	251,695	290,291	312,899
Supplier advance payments		426,607	658,815	542,139	249,234	431,433	701,705	480,709
Other current assets		198,078	310,674	289,250	299,618	255,236	200,288	189,896
Total current assets		7,034,625	7,193,505	6,679,453	5,614,527	7,000,193	8,278,615	8,089,015
Investments		3,787,163	3,752,876	3,777,000	3,750,993	3,841,749	3,802,379	3,828,899
Property, plant and equipment		5,140,106	5,179,868	5,266,408	5,356,434	5,409,151	5,404,347	5,443,079
Other assets		973,885	958,613	1,061,562	1,251,802	970,704	1,072,824	1,069,468
Total assets		16,935,779	17,084,862	16,784,423	15,973,756	17,221,797	18,558,165	18,430,461
Current liabilities:
Notes payable		2,819,086	2,993,456	2,480,264	1,988,215	3,321,808	3,867,438	3,227,564
Current portion of long-term debt		53,056	46,290	71,022	156,345	193,096	205,136	206,894
Customer margin deposits and credit balances		137,999	106,323	139,868	157,914	132,479	149,625	180,850
Customer advance payments		372,616	727,535	414,441	413,163	390,576	871,370	544,266
Accounts payable		1,904,819	1,835,289	2,380,998	1,951,292	1,809,868	1,877,040	2,568,533
Derivative liabilities		344,973	372,406	226,279	316,018	284,212	275,484	317,505
Accrued expenses		538,249	459,867	409,522	437,527	422,371	378,318	389,321
Dividends and equities payable		209,718	128,700	121,209	12,121	134,718	131,380	275,448
Total current liabilities		6,380,516	6,669,866	6,243,603	5,432,595	6,689,128	7,755,791	7,710,381
Long-term debt		1,905,515	1,915,843	1,936,744	2,023,448	2,046,264	2,051,567	1,958,907
Long-term deferred tax liabilities		207,912	171,844	350,841	333,221	350,966	516,681	497,283
Other liabilities		279,303	265,349	315,460	278,667	276,483	272,532	332,610
Commitments and contingencies (Note 15)
Equities:
Preferred stock		2,264,038	2,264,038	2,264,038	2,264,038	2,264,063	2,244,114	2,244,132
Equity certificates		4,253,414	4,307,292	4,319,840	4,341,649	4,214,657	4,201,803	4,208,336
Accumulated other comprehensive loss		(169,726)	(168,225)	(178,445)	(183,670)	(209,700)	(211,442)	(226,220)
Capital reserves		1,803,078	1,646,837	1,520,218	1,471,217	1,577,469	1,713,784	1,691,603		1,604,670
Total CHS Inc. equities		8,150,804	8,049,942	7,925,651	7,893,234	7,846,489	7,948,259	7,917,851
Noncontrolling interests		11,729	12,018	12,124	12,591	12,467	13,335	13,429
Total equities		8,162,533	8,061,960	7,937,775	7,905,825	7,858,956	7,961,594	7,931,280	7,866,250	7,669,411
Total liabilities and equities		16,935,779	17,084,862	16,784,423	15,973,756	17,221,797	18,558,165	18,430,461
Goodwill									160,414
Restatement Adjustments
Current assets:
Cash and cash equivalents		0	28,847	(2,362)	0	(481)	26,336	1,162	10,960	13,904
Receivables		50,002	70,850	(1,401)	22,536	45,642	69,451	(18,906)
Inventories		(27,400)	26,167	65,862	25,019	4,862	(21,536)	25,616
Derivative assets		(233,789)	(178,577)	(116,699)	(13,275)	(182,001)	(153,184)	(141,605)
Margin and related deposits		0	0	0	0	0	0	0
Supplier advance payments		0	0	631	0	0	0	(3,802)
Other current assets		(7,398)	(13,692)	(18,576)	(17,693)	10,233	(4,051)	(2,372)
Total current assets		(218,585)	(66,405)	(72,545)	16,587	(121,745)	(82,984)	(139,907)
Investments		0	0	0	0	0	0	0
Property, plant and equipment		0	0	0	0	(3,500)	0	0
Other assets		(13,645)	(15,061)	(64,160)	(171,421)	(15,172)	(15,951)	(15,014)
Total assets		(232,230)	(81,466)	(136,705)	(154,834)	(140,417)	(98,935)	(154,921)
Current liabilities:
Notes payable		49,420	78,183	0	(3,052)	0	0	0
Current portion of long-term debt		0	0	0	0	0	0	0
Customer margin deposits and credit balances		0	0	0	0	0	0	0
Customer advance payments		(26)	29,107	(922)	10,607	546	26,094	(855)
Accounts payable		(6,647)	18,685	63,652	40,002	55,935	42,381	5,473
Derivative liabilities		(28,142)	(10,497)	(18,853)	(15,072)	(50,257)	(42,977)	(34,847)
Accrued expenses		0	5,165	16,390	17,469	13,740	13,740	8,125
Dividends and equities payable		0	0	0	0	0	0	(35,591)
Total current liabilities		14,605	120,643	60,267	49,954	19,964	39,238	(57,695)
Long-term debt		0	0	0	0	0	0	0
Long-term deferred tax liabilities		(4,704)	(6,185)	(1,939)	(3,241)	18,204	14,841	14,538
Other liabilities		(434)	(321)	(206)	(1,362)	0	0	0
Commitments and contingencies (Note 15)
Equities:
Preferred stock		0	0	0	0	0	0	0
Equity certificates		0	0	0	0	0	0	(13,802)
Accumulated other comprehensive loss		2,424	995	1,104	3,310	1,132	351	1,285
Capital reserves		(244,038)	(196,511)	(195,846)	(203,409)	(179,635)	(153,286)	(99,169)		(119,237)
Total CHS Inc. equities		(241,614)	(195,516)	(194,742)	(200,099)	(178,503)	(152,935)	(111,686)
Noncontrolling interests		(83)	(87)	(85)	(86)	(82)	(79)	(78)
Total equities		(241,697)	(195,603)	(194,827)	(200,185)	(178,585)	(153,014)	(111,764)	(107,091)	(117,972)
Total liabilities and equities		(232,230)	(81,466)	(136,705)	(154,834)	(140,417)	(98,935)	(154,921)
Goodwill									(16,130)
Freight Derivatives and Related Misstatements | Restatement Adjustments
Current assets:
Receivables						500		4,000
Derivative assets		(233,900)	(179,300)	(116,800)	(12,900)	(181,800)	(153,000)	(141,000)
Total assets		(229,300)	(183,800)	(171,700)	(174,100)	(181,600)	(160,300)	(145,500)
Current liabilities:
Accounts payable						7,000	2,300	8,700
Derivative liabilities		(25,600)	(7,100)	(16,500)	(18,000)	(50,300)	(43,000)	(35,000)
Total current liabilities		(50,500)	(26,800)	(38,600)	(39,100)	(64,000)	(61,300)	(47,000)
Long-term deferred tax liabilities		30,400	28,900	30,200	28,900	19,100	15,800	15,500
Equities:
Total equities		(209,200)	185,900	(163,200)	(162,400)	136,800	(114,700)	(114,000)	$ (115,700)	$ (104,600)
Long-term derivative assets				(49,200)	(156,000)
Long-term liabilities		30,400	28,900	30,200	27,500	19,100	15,800	15,500
Goodwill		(16,000)	(16,000)	(16,000)		16,000	(16,000)	(16,000)
Prepaid income taxes		11,100	9,700	8,500	8,900	12,900	6,400	5,700
Prepaid freight capacity		7,500		1,100	1,500	2,000	600	900
Income taxes payable		(24,900)	(19,700)	(22,200)	(21,100)	(20,700)	(20,700)	(20,700)
Derivative liability, noncurrent					(1,400)
Other Misstatements | Restatement Adjustments
Current assets:
Receivables		49,400	78,200
Inventories				67,500	49,200		47,700
Other current assets				(28,100)
Total assets		3,900	108,000	38,400	19,300	41,200	66,300	63,900
Current liabilities:
Notes payable		49,400	78,200
Customer advance payments			29,100				26,100
Accrued expenses				38,600	38,600		34,400
Total current liabilities		72,000	153,100	102,300	89,100	83,900	105,500	74,600
Long-term deferred tax liabilities		(35,100)	(35,100)	(32,100)	(32,100)
Equities:
Total equities		(32,500)	(9,700)	(31,600)	(37,700)	(41,800)	(38,300)	(9,900)
Long-term liabilities		(35,500)	(35,400)	(32,300)	(32,100)	(900)	(900)	(900)
Prepaid income taxes		(24,500)
Income taxes payable		24,900		24,900	24,900	21,000	20,700
Other Misstatements, Net Impact On Income Tax Accounts | Restatement Adjustments
Equities:
Total equities		(14,100)	$ 14,100	20,600	20,600	(24,400)	(24,400)	(28,800)
Other Misstatements, Misclassification | Restatement Adjustments
Current assets:
Inventories					24,100	(48,200)	(48,200)	(48,200)
Total assets					28,100
Current liabilities:
Accounts payable					49,200
Other Misstatements, Timing Difference | Restatement Adjustments
Equities:
Total equities		$ (18,800)						27,900
Other Misstatements, Excise Tax Credit | Restatement Adjustments
Current liabilities:
Accrued expenses				$ 13,700	$ 13,700	$ 13,700	$ 13,700	$ 8,100