Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales and merchandising revenues		$ 1,004,072	$ 836,595	$ 993,662	$ 852,016	$ 1,113,055	$ 859,612	$ 1,064,244	$ 887,879	$ 3,686,345	$ 3,924,790	$ 4,198,495
Interest expense (income)										21,567	21,119	20,072
Equity in earnings of affiliates, net										16,723	9,721	31,924
Other income, net										23,444	14,775	46,472
Income (loss) before income taxes										(20,525)	21,381	(11,564)
Identifiable assets		2,162,354				2,232,849				2,162,354	2,232,849
Capital expenditures										34,602	77,740	72,469
Acquisition of businesses, net of cash acquired and other investments										9,186	2,500	129,299
Depreciation and amortization										86,412	84,325	78,456
Operating Segments | Grain
Segment Reporting Information [Line Items]
Sales and merchandising revenues										2,106,464	2,357,171	2,483,643
Interest expense (income)										8,320	7,955	5,778
Equity in earnings of affiliates, net										4,509	(8,746)	14,703
Other income, net										3,658	5,472	26,229
Income (loss) before income taxes										12,844	(15,651)	(9,446)
Identifiable assets		948,871				961,114				948,871	961,114
Capital expenditures										10,899	21,428	26,862
Acquisition of businesses, net of cash acquired and other investments										5,436	0	0
Depreciation and amortization										18,757	18,232	19,240
Operating Segments | Ethanol
Segment Reporting Information [Line Items]
Sales and merchandising revenues										708,063	544,556	556,188
Interest expense (income)										(67)	35	70
Equity in earnings of affiliates, net										12,214	18,467	17,221
Other income, net										54	77	377
Income (loss) before income taxes										18,878	24,723	28,503
Identifiable assets		180,173				171,115				180,173	171,115
Capital expenditures										3,690	2,301	7,223
Depreciation and amortization										5,970	5,925	5,865
Operating Segments | Plant Nutrient
Segment Reporting Information [Line Items]
Sales and merchandising revenues										651,824	725,176	848,338
Interest expense (income)										6,420	6,448	7,243
Other income, net										5,092	3,716	3,046
Income (loss) before income taxes										(45,121)	14,176	121
Identifiable assets		379,309				484,455				379,309	484,455
Capital expenditures										10,735	15,153	14,384
Acquisition of businesses, net of cash acquired and other investments										0	0	128,549
Depreciation and amortization										26,628	28,663	25,179
Operating Segments | Rail
Segment Reporting Information [Line Items]
Sales and merchandising revenues										172,123	163,658	170,848
Interest expense (income)										7,023	6,461	7,006
Other income, net										2,632	2,218	15,935
Income (loss) before income taxes										24,798	32,428	50,681
Identifiable assets		490,448				398,446				490,448	398,446
Capital expenditures										3,478	4,345	2,990
Depreciation and amortization										23,081	20,082	18,450
Operating Segments | Retail
Segment Reporting Information [Line Items]
Sales and merchandising revenues										47,871	134,229	139,478
Interest expense (income)										324	496	356
Other income, net										10,684	507	557
Income (loss) before income taxes										(7,309)	(8,848)	(455)
Identifiable assets		4,349				31,257				4,349	31,257
Capital expenditures										0	436	1,005
Depreciation and amortization										70	2,452	2,510
Inter-Segments
Segment Reporting Information [Line Items]
Sales and merchandising revenues										2,215	3,507	5,447
Inter-Segments | Grain
Segment Reporting Information [Line Items]
Sales and merchandising revenues										761	1,638	3,573
Inter-Segments | Plant Nutrient
Segment Reporting Information [Line Items]
Sales and merchandising revenues										241	470	682
Inter-Segments | Rail
Segment Reporting Information [Line Items]
Sales and merchandising revenues										1,213	1,399	1,192
Other
Segment Reporting Information [Line Items]
Interest expense (income)										(453)	(276)	(381)
Other income, net										1,324	2,785	328
Income (loss) before income taxes	[1]									(24,713)	(28,323)	(82,713)
Identifiable assets		$ 159,204				$ 186,462				159,204	186,462
Capital expenditures										5,800	34,077	20,005
Acquisition of businesses, net of cash acquired and other investments										3,750	2,500	750
Depreciation and amortization										11,906	8,971	7,212
Non-controlling interest
Segment Reporting Information [Line Items]
Income (loss) before income taxes										$ 98	$ 2,876	$ 1,745

[1] ncludes pension settlement charges in 2015