Segment Reporting - Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2013	May 31, 2012	Aug. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 11,936,556	$ 11,022,955	$ 33,528,872	$ 29,600,926
Cost of goods sold	11,479,645	10,406,699	32,055,796	28,113,086
Gross profit	456,911	616,256	1,473,076	1,487,840
Marketing, general and administrative	138,769	129,224	397,931	368,300
Operating earnings	318,142	487,032	1,075,145	1,119,540
Loss (gain) on investments	(154)		199	446
Interest, net	66,394	71,118	186,989	126,556
Equity income from investments	(27,574)	(24,804)	(72,406)	(68,885)
Income before income taxes	279,476	440,718	960,761	1,061,423
Intersegment Revenue	0	0	0	0
Goodwill	84,166	66,821	84,166	66,821	81,700
Capital expenditures			427,070	315,615
Depreciation and amortization			176,839	161,620
Total identifiable assets	12,877,809	11,473,354	12,877,809	11,473,354	13,423,151
Energy
Segment Reporting Information [Line Items]
Revenues	3,205,340	3,117,272	9,345,304	9,433,098
Cost of goods sold	2,896,061	2,729,383	8,392,704	8,516,284
Gross profit	309,279	387,889	952,600	916,814
Marketing, general and administrative	43,710	41,439	121,364	112,610
Operating earnings	265,569	346,450	831,236	804,204
Loss (gain) on investments
Interest, net	46,058	53,450	124,229	75,755
Equity income from investments	(851)	(1,715)	(580)	(5,658)
Income before income taxes	220,362	294,715	707,587	734,107
Intersegment Revenue	(116,061)	(111,080)	(352,624)	(340,308)
Goodwill	1,165	1,165	1,165	1,165
Capital expenditures			290,091	198,158
Depreciation and amortization			86,454	80,622
Total identifiable assets	4,121,695	3,944,347	4,121,695	3,944,347
Ag Business
Segment Reporting Information [Line Items]
Revenues	8,831,866	7,999,120	24,483,835	20,457,343
Cost of goods sold	8,700,170	7,789,055	24,017,733	19,939,254
Gross profit	131,696	210,065	466,102	518,089
Marketing, general and administrative	77,653	70,208	223,041	203,739
Operating earnings	54,043	139,857	243,061	314,350
Loss (gain) on investments			(45)	446
Interest, net	17,434	14,385	53,472	41,136
Equity income from investments	(3,365)	(6,469)	(13,104)	(16,719)
Income before income taxes	39,974	131,941	202,738	289,487
Goodwill	76,103	58,758	76,103	58,758
Capital expenditures			131,794	113,493
Depreciation and amortization			77,587	66,845
Total identifiable assets	6,913,509	5,865,709	6,913,509	5,865,709
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	15,411	17,643	52,357	50,793
Cost of goods sold	(525)	(659)	(2,017)	(2,144)
Gross profit	15,936	18,302	54,374	52,937
Marketing, general and administrative	17,406	17,577	53,526	51,951
Operating earnings	(1,470)	725	848	986
Loss (gain) on investments	(154)		(154)
Interest, net	2,902	3,283	9,288	9,665
Equity income from investments	(23,358)	(16,620)	(58,722)	(46,508)
Income before income taxes	19,140	14,062	50,436	37,829
Goodwill	6,898	6,898	6,898	6,898
Capital expenditures			5,185	3,964
Depreciation and amortization			12,798	14,153
Total identifiable assets	1,842,605	1,663,298	1,842,605	1,663,298
Reconciling Amounts
Segment Reporting Information [Line Items]
Revenues	(116,061)	(111,080)	(352,624)	(340,308)
Cost of goods sold	(116,061)	(111,080)	(352,624)	(340,308)
Gross profit	0	0	0	0
Operating earnings	0	0	0	0
Income before income taxes	0	0	0	0
Intersegment Revenue	$ 116,061	$ 111,080	$ 352,624	$ 340,308