Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Sales and merchandising revenues	$ 1,138,402	$ 938,660	$ 3,591,369	$ 3,278,501
Inter-segment sales	4,107	4,653	14,409	14,968
Interest expense	5,482	5,711	16,192	20,609
Equity in earnings of affiliates	6,027	9,731	15,406	29,489
Other income, net	3,492	1,217	9,409	5,541
Income (loss) before income taxes	24,324	15,715	98,120	114,919
Identifiable assets	1,991,440	1,458,577	1,991,440	1,458,577	1,734,123
Grain
Segment Reporting Information [Line Items]
Sales and merchandising revenues	677,484	538,723	2,096,256	1,973,820
Inter-segment sales	0	1	1	3
Interest expense	3,465	2,674	9,404	11,373
Equity in earnings of affiliates	9,249	6,459	22,706	18,117
Other income, net	526	652	1,842	1,754
Income (loss) before income taxes	10,807	8,313	45,519	59,955
Identifiable assets	942,629	651,645	942,629	651,645	883,395
Ethanol
Segment Reporting Information [Line Items]
Sales and merchandising revenues	209,634	179,331	528,062	476,783
Inter-segment sales	0	0	0	0
Interest expense	284	194	493	880
Equity in earnings of affiliates	(3,224)	3,270	(7,305)	11,366
Other income, net	1	38	37	133
Income (loss) before income taxes	(936)	4,443	(2,920)	16,844
Identifiable assets	214,858	84,666	214,858	84,666	148,975
Plant Nutrient
Segment Reporting Information [Line Items]
Sales and merchandising revenues	135,144	137,637	619,301	521,109
Inter-segment sales	3,481	4,224	11,898	12,830
Interest expense	725	940	2,067	2,756
Equity in earnings of affiliates	2	2	5	6
Other income, net	523	282	1,651	541
Income (loss) before income taxes	759	6,622	34,540	35,813
Identifiable assets	268,982	302,399	268,982	302,399	240,543
Rail
Segment Reporting Information [Line Items]
Sales and merchandising revenues	59,703	24,067	127,608	82,478
Inter-segment sales	105	111	516	486
Interest expense	1,229	1,614	3,563	4,572
Equity in earnings of affiliates	0	0	0	0
Other income, net	1,695	604	3,295	2,198
Income (loss) before income taxes	19,071	1,123	34,288	7,432
Identifiable assets	309,847	217,335	309,847	217,335	246,188
Turf and Specialty
Segment Reporting Information [Line Items]
Sales and merchandising revenues	21,509	23,051	110,481	111,872
Inter-segment sales	521	317	1,994	1,649
Interest expense	238	273	906	1,094
Equity in earnings of affiliates	0	0	0	0
Other income, net	181	167	671	716
Income (loss) before income taxes	(1,571)	(1,245)	3,384	3,811
Identifiable assets	55,638	54,165	55,638	54,165	69,487
Retail
Segment Reporting Information [Line Items]
Sales and merchandising revenues	34,928	35,851	109,661	112,439
Inter-segment sales	0	0	0	0
Interest expense	217	238	570	705
Equity in earnings of affiliates	0	0	0	0
Other income, net	117	130	396	430
Income (loss) before income taxes	(1,769)	(1,233)	(3,090)	(2,020)
Identifiable assets	56,795	54,971	56,795	54,971	52,018
Other
Segment Reporting Information [Line Items]
Sales and merchandising revenues	0	0	0	0
Inter-segment sales	0	0	0	0
Interest expense	(676)	(222)	(811)	(771)
Equity in earnings of affiliates	0	0	0	0
Other income, net	449	(656)	1,517	(231)
Income (loss) before income taxes	(344)	(2,614)	(10,501)	(8,161)
Identifiable assets	142,691	93,396	142,691	93,396	93,517
Noncontrolling Interest
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ (1,693)	$ 306	$ (3,100)	$ 1,245