Quarterly Financial Information (Unaudited) - Impacts of the Restatement Adjustments to the Previously Reported Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Feb. 28, 2018	Feb. 28, 2017	May 31, 2018	May 31, 2017	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues	$ 8,583,982	$ 9,087,328	$ 6,980,153	$ 8,031,884	$ 7,996,339	$ 8,638,410	$ 7,400,773	$ 8,001,904	$ 15,012,037	$ 15,402,677	$ 24,099,365	$ 24,041,087	$ 32,683,347	$ 32,037,426	$ 30,355,260
Cost of goods sold	8,192,620	8,841,361	6,844,849	7,711,057	7,904,713	8,417,264	7,165,265	7,655,524	14,555,906	14,820,789	23,397,267	23,238,053	31,589,887	31,142,766	29,386,515
Gross profit	391,362	245,967	135,304	320,827	91,626	221,146	235,508	346,380	456,131	581,888	702,098	803,034	1,093,460	894,660	968,745
Marketing, general and administrative	186,291	161,579	186,713	139,500	145,236	155,347	160,166	151,258	326,213	311,424	487,792	466,771	674,083	612,007	601,266
Reserve and impairment charges (recoveries), net	(18,765)	(3,811)	(11,346)	(3,787)	39,170	326,779	72,373	18,357	(15,133)	90,730	(18,944)	417,509	(37,709)	456,679	75,036
Operating earnings (loss)	223,836	88,199	(40,063)	185,114	(92,780)	(260,980)	2,969	176,765	145,051	179,734	233,250	(81,246)	457,086	(174,026)	292,443
(Gain) loss on disposal of business	(61)	(124,050)	(7,705)	0	704	(1,224)	(1,395)	4,105	(7,705)	2,710	(131,755)	1,486	(131,816)	2,190	0
Interest expense	18,984	49,340	40,176	40,702	53,828	39,201	39,945	38,265	80,878	78,210	130,218	117,411	149,202	171,239	113,704
Other (income) loss	(27,015)	(14,622)	(11,364)	(25,014)	(25,407)	(11,952)	(18,083)	(44,509)	(36,378)	(62,592)	(51,000)	(74,544)	(78,015)	(99,951)	(47,609)
Equity (income) loss from investments	(16,404)	(59,308)	(39,441)	(38,362)	(12,817)	(48,393)	(35,800)	(40,328)	(77,803)	(76,128)	(137,111)	(124,521)	(153,515)	(137,338)	(175,777)
Income (loss) before income taxes	248,332	236,839	(21,729)	207,788	(109,088)	(238,612)	18,302	219,232	186,059	237,534	422,898	(1,078)	671,230	(110,166)	402,125
Income tax expense (benefit)	7,787	55,219	(187,688)	20,606	(34,761)	(166,124)	3,685	16,076	(167,082)	19,761	(111,863)	(146,363)	(104,076)	(181,124)	19,099
Net income (loss)	240,545	181,620	165,959	187,182	(74,327)	(72,488)	14,617	203,156	353,141	217,773	534,761	145,285	775,306	70,958	383,026
Net income (loss) attributable to noncontrolling interests	98	(187)	(48)	(464)	123	(955)	406	(208)	(512)	198	(699)	(757)	(601)	(634)	(223)
Comprehensive income attributable to CHS Inc.	$ 240,447	181,807	166,007	187,646	(74,450)	(71,533)	14,211	203,364	353,653	217,575	535,460	146,042	$ 775,907	71,592	383,249
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		9,027,525	6,851,093	8,048,889	7,952,005	8,614,090	7,320,406	8,048,250	14,899,982	15,368,656	23,927,508	23,982,746		31,934,751	30,347,203
Cost of goods sold		8,728,914	6,708,610	7,735,627	7,843,305	8,366,988	7,079,664	7,695,553	14,444,237	14,775,217	23,173,151	23,142,205		30,985,510	29,387,910
Gross profit		298,611	142,483	313,262	108,700	247,102	240,742	352,697	455,745	593,439	754,357	840,541		949,241	959,293
Marketing, general and administrative		161,578	186,716	140,168	144,528	153,498	157,862	147,849	326,881	305,711	488,459	459,831		604,359	601,261
Reserve and impairment charges (recoveries), net		(3,811)	(11,349)	(3,787)	42,670	323,901	72,373	18,357	(15,133)	90,730	(18,944)	414,009		456,679	47,836
Operating earnings (loss)		140,844	(32,884)	176,881	(78,498)	(230,297)	10,507	186,491	143,997	196,998	284,842	(33,299)		(111,797)	310,196
(Gain) loss on disposal of business		(124,050)	(7,705)		0	0	0	0	(7,705)	0	(131,755)	0		0	0
Interest expense		49,340	40,176	40,702	53,828	39,201	39,945	38,265	80,878	78,210	130,218	117,411		171,239	113,704
Other (income) loss		(14,622)	(11,364)	(25,014)	(24,664)	(11,947)	(17,235)	(37,000)	(36,378)	(54,235)	(51,000)	(66,183)		(90,846)	(47,609)
Equity (income) loss from investments		(59,308)	(39,441)	(38,362)	(12,817)	(48,393)	(35,800)	(40,328)	(77,803)	(76,128)	(137,111)	(124,521)		(137,338)	(175,777)
Income (loss) before income taxes		289,484	(14,550)	199,555	(94,845)	(209,158)	23,597	225,554	185,005	249,151	474,490	39,994		(54,852)	419,878
Income tax expense (benefit)		60,338	(181,176)	19,936	(44,293)	(163,018)	8,624	16,612	(161,240)	25,236	(100,901)	(137,781)		(182,075)	(4,091)
Net income (loss)		229,146	166,626	179,619	(50,552)	(46,140)	14,973	208,942	346,245	223,915	575,391	177,775		127,223	423,969
Net income (loss) attributable to noncontrolling interests		(187)	(48)	(464)	123	(955)	406	(208)	(512)	198	(699)	(757)		(634)	(223)
Comprehensive income attributable to CHS Inc.		229,333	166,674	180,083	(50,675)	(45,185)	14,567	209,150	346,757	223,717	576,090	178,532		127,857	424,192
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		59,803	129,060	(17,005)	44,334	24,320	80,367	(46,346)	112,055	34,021	171,857	58,341		102,675	8,057
Cost of goods sold		112,447	136,239	(24,570)	61,408	50,276	85,601	(40,029)	111,669	45,572	224,116	95,848		157,256	(1,395)
Gross profit		(52,644)	(7,179)	7,565	(17,074)	(25,956)	(5,234)	(6,317)	386	(11,551)	(52,259)	(37,507)		(54,581)	9,452
Marketing, general and administrative		1	(3)	(668)	708	1,849	2,304	3,409	(668)	5,713	(667)	6,940		7,648	5
Reserve and impairment charges (recoveries), net		0	3	0	(3,500)	2,878	0	0	0	0	0	3,500		0	27,200
Operating earnings (loss)		(52,645)	(7,179)	8,233	(14,282)	(30,683)	(7,538)	(9,726)	1,054	(17,264)	(51,592)	(47,947)		(62,229)	(17,753)
(Gain) loss on disposal of business		0	0		704	(1,224)	(1,395)	4,105	0	2,710	0	1,486		2,190	0
Interest expense		0	0	0	0	0	0	0	0	0	0	0		0	0
Other (income) loss		0	0	0	(743)	(5)	(848)	(7,509)	0	(8,357)	0	(8,361)		(9,105)	0
Equity (income) loss from investments		0	0	0	0	0	0	0	0	0	0	0		0	0
Income (loss) before income taxes		(52,645)	(7,179)	8,233	(14,243)	(29,454)	(5,295)	(6,322)	1,054	(11,617)	(51,592)	(41,072)		(55,314)	(17,753)
Income tax expense (benefit)		(5,119)	(6,512)	670	9,532	(3,106)	(4,939)	(536)	(5,842)	(5,475)	(10,962)	(8,582)		951	23,190
Net income (loss)		(47,526)	(667)	7,563	(23,775)	(26,348)	(356)	(5,786)	6,896	(6,142)	(40,630)	(32,490)		(56,265)	(40,943)
Net income (loss) attributable to noncontrolling interests		0	0	0	0	0	0	0	0	0	0	0		0	0
Comprehensive income attributable to CHS Inc.		(47,526)	(667)	7,563	(23,775)	(26,348)	(356)	(5,786)	6,896	(6,142)	(40,630)	(32,490)		(56,265)	(40,943)
Freight Derivatives and Related Misstatements | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues					2,900	(3,700)	(1,100)	1,900		700		(2,900)
Cost of goods sold		29,800	22,500	500	14,900	22,200	(900)	1,900	23,000	1,000	52,900	23,200		38,100	15,700
Income (loss) before income taxes		(29,800)	(22,500)	(500)	(12,000)	(25,900)	(300)	100	(23,000)	(200)	(52,900)	(26,200)		(38,100)	(15,700)
Income tax expense (benefit)		(5,100)	100	700	13,300	(3,100)	(500)	(600)	800	(1,000)	(4,400)	(4,100)		9,200	(5,800)
Net income (loss)		(24,700)	(22,600)	(1,200)	(25,200)	(22,800)	200	600	(23,800)	800	(48,500)	(22,100)		(47,300)	(9,900)
Intercompany Misstatements | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		38,800	161,500	(11,400)	(7,700)			(77,300)	150,200		189,000	(28,000)		(35,700)	(57,500)
Cost of goods sold		38,800	161,500	11,400	(7,700)	(9,600)	(58,900)	(77,300)	150,200	(18,400)	189,000	(28,000)		(35,700)	(57,500)
Other Misstatements | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues			(28,000)			(9,600)	58,900	29,100		(18,400)
Cost of goods sold		18,800	(1,600)				5,600	29,100		12,100
Marketing, general and administrative								3,400
Reserve and impairment charges (recoveries), net					(3,500)	3,500						3,500
(Gain) loss on disposal of business								4,100
Other (income) loss								(7,500)
Income (loss) before income taxes		(22,800)	15,300	8,800	(2,300)	(3,600)	(5,000)	(6,400)	24,100	(11,400)	1,300	(14,900)		(17,200)	(2,100)
Income tax expense (benefit)			(6,600)		(3,700)		(4,500)		(6,600)	(4,500)	(6,600)	(4,500)		(8,200)	29,000
Net income (loss)		(22,800)	21,900	8,800	1,400	(3,600)	(600)	$ (6,400)	30,700	(6,900)	7,900	(10,400)		(9,000)	(31,000)
Other Misstatements, Timing Of Revenue Recognition | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		11,800									7,000
Cost of goods sold		14,500									9,900
Other Misstatements, Timing Difference | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of goods sold					2,600						18,800
Other Misstatements, Misclassification | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		9,200		(5,700)	49,100	37,600	22,600		(33,400)	51,700	(24,100)	89,200
Cost of goods sold		9,200	27,700	5,700	49,100	37,600	22,500		33,400	51,600	24,100	89,200
Marketing, general and administrative						1,800	2,300			5,700		6,900
Reserve and impairment charges (recoveries), net						600
(Gain) loss on disposal of business					700	$ (1,200)	(1,400)			2,700		(1,500)
Other (income) loss					(700)		(800)			(8,400)		(8,400)
Other Misstatements, Excise Tax Credit | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of goods sold			$ (13,700)						(13,700)		(13,700)	12,100
Other Misstatements, Valuation of Derivatives | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of goods sold		$ 1,300		(6,200)	$ 3,200		$ (600)		(7,900)	$ (700)	(6,600)	$ (700)		$ 2,500	$ 400
Other Misstatements, Postretirement Benefit Plan Activity | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of goods sold				$ (2,600)					$ 2,600		$ (2,600)