Segment Reporting - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014	Aug. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 8,740,905	$ 11,967,398	$ 26,596,101	$ 32,673,793
Cost of goods sold	8,430,249	11,460,774	25,450,359	31,324,819
Gross profit	310,656	506,624	1,145,742	1,348,974
Marketing, general and administrative	165,341	158,859	498,084	447,771
Operating earnings	145,315	347,765	647,658	901,203
Loss (gain) on investments	0	(108,792)	(5,074)	(111,401)
Interest, net	9,557	42,489	39,648	102,263
Equity (income) loss from investments	(34,750)	(25,522)	(83,548)	(89,249)
Income before income taxes	170,508	439,590	696,632	999,590
Intersegment revenues	0	0	0	0
Acquisition of property, plant and equipment			827,228	656,288
Depreciation and amortization			227,323	193,161
Total assets	15,719,259	14,944,947	15,719,259	14,944,947	$ 15,146,979
Energy [Member]
Segment Reporting Information [Line Items]
Revenues	1,732,192	2,862,239	6,697,942	9,064,748
Cost of goods sold	1,618,937	2,603,480	6,217,789	8,351,509
Gross profit	113,255	258,759	480,153	713,239
Marketing, general and administrative	37,956	37,915	118,082	108,012
Operating earnings	75,299	220,844	362,071	605,227
Loss (gain) on investments	0	0	0	0
Interest, net	(7,678)	23,952	(11,121)	54,974
Equity (income) loss from investments	(364)	(780)	(1,440)	(2,937)
Income before income taxes	83,341	197,672	374,632	553,190
Intersegment revenues	(94,092)	(141,501)	(374,612)	(436,522)
Acquisition of property, plant and equipment			467,700	367,044
Depreciation and amortization			104,984	99,546
Total assets	4,600,786	4,203,832	4,600,786	4,203,832
Ag [Member]
Segment Reporting Information [Line Items]
Revenues	7,088,072	9,236,768	20,231,391	24,001,467
Cost of goods sold	6,908,435	9,007,141	19,619,374	23,418,189
Gross profit	179,637	229,627	612,017	583,278
Marketing, general and administrative	111,438	102,224	321,986	288,992
Operating earnings	68,199	127,403	290,031	294,286
Loss (gain) on investments	0	0	(2,875)	116
Interest, net	14,478	15,449	43,284	39,736
Equity (income) loss from investments	(7,964)	(5,216)	(12,427)	(19,906)
Income before income taxes	61,685	117,170	262,049	274,340
Intersegment revenues	(3,017)	(8,303)	(12,166)	(8,303)
Acquisition of property, plant and equipment			305,136	250,607
Depreciation and amortization			112,252	85,315
Total assets	8,033,290	7,370,032	8,033,290	7,370,032
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	17,750	18,195	53,546	52,403
Cost of goods sold	(14)	(43)	(26)	(54)
Gross profit	17,764	18,238	53,572	52,457
Marketing, general and administrative	15,947	18,720	58,016	50,767
Operating earnings	1,817	(482)	(4,444)	1,690
Loss (gain) on investments	0	(108,792)	(2,199)	(111,517)
Interest, net	2,757	3,088	7,485	7,553
Equity (income) loss from investments	(26,422)	(19,526)	(69,681)	(66,406)
Income before income taxes	25,482	124,748	59,951	172,060
Intersegment revenues	0	0	0	0
Acquisition of property, plant and equipment			54,392	38,637
Depreciation and amortization			10,087	8,300
Total assets	3,085,183	3,371,083	3,085,183	3,371,083
Reconciling Amounts
Segment Reporting Information [Line Items]
Revenues	(97,109)	(149,804)	(386,778)	(444,825)
Cost of goods sold	(97,109)	(149,804)	(386,778)	(444,825)
Gross profit	0	0	0	0
Marketing, general and administrative	0	0	0	0
Operating earnings	0	0	0	0
Loss (gain) on investments	0	0	0	0
Interest, net	0	0	0	0
Equity (income) loss from investments	0	0	0	0
Income before income taxes	0	0	0	0
Intersegment revenues	97,109	149,804	386,778	444,825
Acquisition of property, plant and equipment			0	0
Depreciation and amortization			0	0
Total assets	$ 0	$ 0	$ 0	$ 0