Segment Reporting - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016	Aug. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 7,320,406	$ 6,639,330	$ 15,368,656	$ 14,368,122
Operating earnings (loss)	10,507	(91,803)	196,998	168,011
(Gain) loss on investments	(2,782)	(3,050)	4,619	(8,722)
Interest expense	39,945	25,036	78,210	34,087
Other income	(14,453)	(9,323)	(58,854)	(11,381)
Equity (income) loss from investments	(35,800)	(28,004)	(76,128)	(59,366)
Income (loss) before income taxes	23,597	(76,462)	249,151	213,393
Total assets	18,558,165		18,558,165		$ 17,312,135
Energy [Member]
Segment Reporting Information [Line Items]
Revenues	1,529,034	1,134,148	3,229,214	2,840,061
Operating earnings (loss)	19,506	(69,299)	92,286	111,213
(Gain) loss on investments	0	0	0	0
Interest expense	3,565	(4,854)	7,833	(16,453)
Other income	(187)	46	(496)	43
Equity (income) loss from investments	(486)	(1,364)	(1,648)	(2,187)
Income (loss) before income taxes	16,614	(63,127)	86,597	129,810
Total assets	4,388,668		4,388,668
Ag [Member]
Segment Reporting Information [Line Items]
Revenues	5,855,331	5,580,450	12,291,325	11,694,706
Operating earnings (loss)	(14,291)	(21,818)	95,306	53,173
(Gain) loss on investments	(690)	(42)	6,695	(5,714)
Interest expense	16,850	16,485	33,189	33,267
Other income	(17,686)	(8,493)	(35,609)	(10,305)
Equity (income) loss from investments	(3,455)	1,355	(8,872)	(2,221)
Income (loss) before income taxes	(9,310)	(31,123)	99,903	38,146
Total assets	8,093,289		8,093,289
Nitrogen Production [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Operating earnings (loss)	(4,385)	(5,759)	(8,414)	(5,759)
(Gain) loss on investments	0	0	0	0
Interest expense	12,182	4,737	24,918	4,737
Other income	(464)	0	(29,570)	0
Equity (income) loss from investments	(21,557)	(11,855)	(36,253)	(11,855)
Income (loss) before income taxes	5,454	1,359	32,491	1,359
Total assets	2,809,029		2,809,029
Foods [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Operating earnings (loss)	(2,472)	(2,125)	(5,269)	(4,076)
(Gain) loss on investments	0	0	0	0
Interest expense	0	779	0	1,601
Other income	0	0	0	0
Equity (income) loss from investments	(5,561)	(14,450)	(18,930)	(35,527)
Income (loss) before income taxes	3,089	11,546	13,661	29,850
Total assets	370,089		370,089
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	31,430	23,201	58,871	43,096
Operating earnings (loss)	12,149	7,198	23,089	13,460
(Gain) loss on investments	(2,092)	(3,008)	(2,076)	(3,008)
Interest expense	11,411	7,280	19,385	10,935
Other income	(179)	(267)	(294)	(1,119)
Equity (income) loss from investments	(4,741)	(1,690)	(10,425)	(7,576)
Income (loss) before income taxes	7,750	4,883	16,499	14,228
Total assets	2,897,090		2,897,090
Reconciling Amounts
Segment Reporting Information [Line Items]
Revenues	(95,389)	(98,469)	(210,754)	(209,741)
Operating earnings (loss)	0	0	0	0
(Gain) loss on investments	0	0	0	0
Interest expense	(4,063)	609	(7,115)	0
Other income	4,063	(609)	7,115	0
Equity (income) loss from investments	0	0	0	0
Income (loss) before income taxes	0	0	0	0
Total assets	0		0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations [Member] | Energy [Member]
Segment Reporting Information [Line Items]
Revenues	(89,094)	(67,208)	(199,181)	(174,311)
Intersegment Eliminations [Member] | Ag [Member]
Segment Reporting Information [Line Items]
Revenues	(4,758)	(29,963)	(8,523)	(33,016)
Intersegment Eliminations [Member] | Nitrogen Production [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations [Member] | Foods [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations [Member] | Corporate and Other
Segment Reporting Information [Line Items]
Revenues	(1,537)	(1,298)	(3,050)	(2,414)
Intersegment Eliminations [Member] | Reconciling Amounts
Segment Reporting Information [Line Items]
Revenues	$ 95,389	$ 98,469	$ 210,754	$ 209,741