Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales and merchandising revenues	$ 1,181,374	$ 1,138,402	$ 4,020,308	$ 3,591,369
Inter-segment sales	4,868	4,107	18,475	14,409
Interest expense	5,348	5,482	16,607	16,192
Equity in earnings (loss) of affiliates	22,177	6,027	39,991	15,406
Other income (expense), net	7,605	3,492	11,623	9,409
Income (loss) before income taxes	28,387	24,324	97,990	98,120
Identifiable assets	1,882,291	1,991,440	1,882,291	1,991,440	2,182,304
Grain
Segment Reporting Information [Line Items]
Sales and merchandising revenues	765,833	677,484	2,493,678	2,096,256
Inter-segment sales	0	0	333	1
Interest expense	1,391	3,465	7,714	9,404
Equity in earnings (loss) of affiliates	12,003	9,249	24,940	22,706
Other income (expense), net	1,216	526	1,438	1,842
Income (loss) before income taxes	14,323	10,807	24,675	45,519
Identifiable assets	784,869	942,629	784,869	942,629	1,076,986
Ethanol
Segment Reporting Information [Line Items]
Sales and merchandising revenues	213,384	209,634	634,933	528,062
Interest expense	289	284	895	493
Equity in earnings (loss) of affiliates	10,174	(3,224)	15,051	(7,305)
Other income (expense), net	35	1	465	37
Income (loss) before income taxes	10,904	(936)	23,984	(2,920)
Identifiable assets	207,530	214,858	207,530	214,858	206,975
Plant Nutrient
Segment Reporting Information [Line Items]
Sales and merchandising revenues	95,681	135,144	537,922	619,301
Inter-segment sales	4,243	3,481	15,955	11,898
Interest expense	746	725	2,461	2,067
Equity in earnings (loss) of affiliates	0	2	0	5
Other income (expense), net	320	523	459	1,651
Income (loss) before income taxes	(1,643)	759	21,035	34,540
Identifiable assets	258,772	268,982	258,772	268,982	257,980
Rail
Segment Reporting Information [Line Items]
Sales and merchandising revenues	47,523	59,703	132,488	127,608
Inter-segment sales	109	105	318	516
Interest expense	1,220	1,229	4,162	3,563
Other income (expense), net	5,031	1,695	6,679	3,295
Income (loss) before income taxes	12,360	19,071	36,614	34,288
Identifiable assets	294,528	309,847	294,528	309,847	289,467
Turf and Specialty
Segment Reporting Information [Line Items]
Sales and merchandising revenues	27,624	21,509	117,955	110,481
Inter-segment sales	516	521	1,869	1,994
Interest expense	203	238	951	906
Other income (expense), net	135	181	585	671
Income (loss) before income taxes	(83)	(1,571)	6,113	3,384
Identifiable assets	71,600	55,638	71,600	55,638	82,683
Retail
Segment Reporting Information [Line Items]
Sales and merchandising revenues	31,329	34,928	103,332	109,661
Interest expense	152	217	519	570
Other income (expense), net	102	117	316	396
Income (loss) before income taxes	(2,043)	(1,769)	(3,673)	(3,090)
Identifiable assets	51,465	56,795	51,465	56,795	51,772
Other
Segment Reporting Information [Line Items]
Interest expense	1,347	(676)	(95)	(811)
Other income (expense), net	766	449	1,681	1,517
Income (loss) before income taxes	(6,309)	(344)	(12,563)	(10,501)
Identifiable assets	213,527	142,691	213,527	142,691	216,441
Noncontrolling Interests
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ 878	$ (1,693)	$ 1,805	$ (3,100)