Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total Revenues	$ 812,662	$ 685,579	$ 911,402	$ 635,739	$ 1,004,072	$ 836,595	$ 993,662	$ 852,016	$ 3,045,382	$ 3,686,345	$ 3,924,790
Interest expense (income)									27,848	21,567	21,119
Equity in earnings of affiliates, net									27,141	16,723	9,721
Other income, net									16,002	22,507	12,473
Income (loss) before income taxes									53,156	(20,525)	21,381
Identifiable assets	2,392,003				2,162,354				2,392,003	2,162,354
Capital expenditures									142,579	34,602	77,740
Acquisition of businesses, net of cash acquired, and other investments									3,334	9,186	2,500
Depreciation and amortization									90,297	86,412	84,325
Operating Segments | Grain
Segment Reporting Information [Line Items]
Total Revenues									1,436,979	2,106,464	2,357,171
Interest expense (income)									11,843	8,320	7,955
Equity in earnings of affiliates, net									12,932	4,509	(8,746)
Other income, net									2,959	3,658	5,472
Income (loss) before income taxes									26,676	12,844	(15,651)
Identifiable assets	978,974				948,871				978,974	948,871
Capital expenditures									17,203	10,899	21,428
Acquisition of businesses, net of cash acquired, and other investments									2,248	5,436	0
Depreciation and amortization									16,062	18,757	18,232
Operating Segments | Ethanol
Segment Reporting Information [Line Items]
Total Revenues									743,690	708,063	544,556
Interest expense (income)									(1,888)	(67)	35
Equity in earnings of affiliates, net									14,209	12,214	18,467
Other income, net									650	54	77
Income (loss) before income taxes									22,115	18,878	24,723
Identifiable assets	295,971				180,173				295,971	180,173
Capital expenditures									101,320	3,690	2,301
Depreciation and amortization									6,136	5,970	5,925
Operating Segments | Plant Nutrient
Segment Reporting Information [Line Items]
Total Revenues									690,536	651,824	725,176
Interest expense (income)									6,499	6,420	6,448
Other income, net									2,495	5,092	3,716
Income (loss) before income taxes									12,030	(45,121)	14,176
Identifiable assets	403,780				379,309				403,780	379,309
Capital expenditures									15,723	10,735	15,153
Depreciation and amortization									26,871	26,628	28,663
Operating Segments | Rail
Segment Reporting Information [Line Items]
Total Revenues									174,177	172,123	163,658
Interest expense (income)									11,377	7,023	6,461
Other income, net									3,516	2,632	2,218
Income (loss) before income taxes									17,379	24,798	32,428
Identifiable assets	590,407				490,448				590,407	490,448
Capital expenditures									5,295	3,478	4,345
Depreciation and amortization									29,164	23,081	20,082
Inter-Segments
Segment Reporting Information [Line Items]
Total Revenues									3,951	2,215	3,507
Inter-Segments | Grain
Segment Reporting Information [Line Items]
Total Revenues									2,746	761	1,638
Inter-Segments | Plant Nutrient
Segment Reporting Information [Line Items]
Total Revenues									0	241	470
Inter-Segments | Rail
Segment Reporting Information [Line Items]
Total Revenues									1,205	1,213	1,399
Other
Segment Reporting Information [Line Items]
Total Revenues									0	47,871	134,229
Interest expense (income)									17	(129)	220
Other income, net									6,382	11,071	990
Income (loss) before income taxes									(24,785)	(32,022)	(37,171)
Identifiable assets	$ 122,871				$ 163,553				122,871	163,553
Capital expenditures									3,038	5,800	34,513
Acquisition of businesses, net of cash acquired, and other investments									1,086	3,750	2,500
Depreciation and amortization									12,064	11,976	11,423
Non-controlling interest
Segment Reporting Information [Line Items]
Income (loss) before income taxes									$ (259)	$ 98	$ 2,876