Segment Reporting - Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012	Aug. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 9,882,378	$ 8,843,812	$ 21,592,316	$ 18,577,971
Cost of goods sold	9,411,731	8,612,235	20,576,151	17,706,387
Gross profit	470,647	231,577	1,016,165	871,584
Marketing, general and administrative	134,680	126,556	259,162	239,076
Operating earnings	335,967	105,021	757,003	632,508
Loss (gain) on investments	(45)	484	(45)	446
Interest, net	53,385	34,631	120,595	55,438
Equity income from investments	(16,760)	(19,952)	(44,832)	(44,081)
Income before income taxes	299,387	89,858	681,285	620,705
Intersegment Revenue	0	0	0	0
Goodwill	88,147	78,201	88,147	78,201	81,700
Capital expenditures			264,332	197,887
Depreciation and amortization			116,912	104,732
Total identifiable assets	12,953,201	11,366,995	12,953,201	11,366,995	13,423,151
Energy
Segment Reporting Information [Line Items]
Revenues	2,815,736	2,918,852	6,139,964	6,315,826
Cost of goods sold	2,505,801	2,821,733	5,496,643	5,786,901
Gross profit	309,935	97,119	643,321	528,925
Marketing, general and administrative	41,183	38,268	77,654	71,171
Operating earnings	268,752	58,851	565,667	457,754
Loss (gain) on investments
Interest, net	32,388	18,803	78,171	22,305
Equity income from investments	2,155	(2,053)	271	(3,943)
Income before income taxes	234,209	42,101	487,225	439,392
Intersegment Revenue	(102,957)	(99,098)	(236,563)	(229,228)
Goodwill	1,165	1,165	1,165	1,165
Capital expenditures			173,669	126,200
Depreciation and amortization			57,256	53,031
Total identifiable assets	3,648,852	3,803,977	3,648,852	3,803,977
Ag Business
Segment Reporting Information [Line Items]
Revenues	7,150,228	6,008,402	15,651,969	12,458,223
Cost of goods sold	7,009,448	5,890,328	15,317,563	12,150,199
Gross profit	140,780	118,074	334,406	308,024
Marketing, general and administrative	74,401	71,688	145,388	133,531
Operating earnings	66,379	46,386	189,018	174,493
Loss (gain) on investments	(45)	484	(45)	446
Interest, net	17,826	12,837	36,038	26,751
Equity income from investments	(1,792)	(3,088)	(9,739)	(10,250)
Income before income taxes	50,390	36,153	162,764	157,546
Goodwill	80,084	70,138	80,084	70,138
Capital expenditures			87,466	68,716
Depreciation and amortization			51,072	42,242
Total identifiable assets	7,493,776	5,694,095	7,493,776	5,694,095
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	19,371	15,656	36,946	33,150
Cost of goods sold	(561)	(728)	(1,492)	(1,485)
Gross profit	19,932	16,384	38,438	34,635
Marketing, general and administrative	19,096	16,600	36,120	34,374
Operating earnings	836	(216)	2,318	261
Loss (gain) on investments
Interest, net	3,171	2,991	6,386	6,382
Equity income from investments	(17,123)	(14,811)	(35,364)	(29,888)
Income before income taxes	14,788	11,604	31,296	23,767
Goodwill	6,898	6,898	6,898	6,898
Capital expenditures			3,197	2,971
Depreciation and amortization			8,584	9,459
Total identifiable assets	1,810,573	1,868,923	1,810,573	1,868,923
Reconciling Amounts
Segment Reporting Information [Line Items]
Revenues	(102,957)	(99,098)	(236,563)	(229,228)
Cost of goods sold	(102,957)	(99,098)	(236,563)	(229,228)
Gross profit	0	0	0	0
Operating earnings	0	0	0	0
Income before income taxes	0	0	0	0
Intersegment Revenue	$ 102,957	$ 99,098	$ 236,563	$ 229,228