Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales and merchandising revenues	$ 1,271,768	$ 952,927	$ 1,312,082	$ 1,003,294	$ 1,584,266	$ 1,181,374	$ 1,566,964	$ 1,271,970	$ 4,540,071	$ 5,604,574	$ 5,272,010
Segment Reporting, Measurement for Transactions Between Reportable Segments									24872	20220	19516
Interest expense (income)									21,760	20,860	22,155
Equity in earnings of affiliates, net									96,523	68,705	16,487
Other income, net									31,125	14,876	14,725
Income (loss) before income taxes									184,146	149,513	120,133
Identifiable assets	2,364,692				2,273,556				2,364,692	2,273,556
Capital expenditures									59,675	46,786	69,017
Acquisition of businesses, net of cash acquired and investments in affiliates									55,795	64,501	220,257
Depreciation and amortization									62,005	55,307	48,977
Grain
Segment Reporting Information [Line Items]
Sales and merchandising revenues									2,682,038	3,617,943	3,293,632
Inter-segment sales									251,000	220,000	261,800
Segment Reporting, Measurement for Transactions Between Reportable Segments									5066	1	409
Interest expense (income)									8,785	9,567	12,174
Equity in earnings of affiliates, net									27,643	33,122	29,080
Other income, net									21,450	2,120	2,548
Income (loss) before income taxes									58,136	46,805	63,597
Identifiable assets	1,137,437				921,914				1,137,437	921,914
Capital expenditures									20,958	8,535	30,178
Acquisition of businesses, net of cash acquired and investments in affiliates									40,206	51,544	116,888
Depreciation and amortization									16,547	15,620	9,554
Ethanol
Segment Reporting Information [Line Items]
Sales and merchandising revenues									765,939	831,965	742,929
Interest expense (income)									255	1,038	759
Equity in earnings of affiliates, net									68,880	35,583	(12,598)
Other income, net									223	399	53
Income (loss) before income taxes									92,257	50,600	(3,720)
Identifiable assets	197,888				229,797				197,888	229,797
Capital expenditures									2,256	4,052	1,966
Acquisition of businesses, net of cash acquired and investments in affiliates									0	0	77,400
Depreciation and amortization									5,700	5,909	5,003
Plant Nutrient
Segment Reporting Information [Line Items]
Sales and merchandising revenues									668,124	708,654	797,033
Segment Reporting, Measurement for Transactions Between Reportable Segments									16829	17537	16135
Interest expense (income)									3,736	3,312	2,832
Equity in earnings of affiliates, net									0	0	5
Other income, net									3,262	1,093	1,917
Income (loss) before income taxes									23,845	27,275	39,254
Identifiable assets	330,731				268,238				330,731	268,238
Capital expenditures									18,372	17,094	18,038
Acquisition of businesses, net of cash acquired and investments in affiliates									15,489	0	15,286
Depreciation and amortization									15,294	14,143	12,014
Rail
Segment Reporting Information [Line Items]
Sales and merchandising revenues									148,954	164,794	156,426
Segment Reporting, Measurement for Transactions Between Reportable Segments									466	427	622
Interest expense (income)									7,247	5,544	4,807
Other income, net									3,094	7,666	7,136
Income (loss) before income taxes									31,445	42,785	42,841
Identifiable assets	365,531				312,654				365,531	312,654
Capital expenditures									2,332	4,135	3,896
Acquisition of businesses, net of cash acquired and investments in affiliates									0	7,804	0
Depreciation and amortization									13,262	12,031	15,929
Turf & Specialty
Segment Reporting Information [Line Items]
Sales and merchandising revenues									134,209	140,512	131,026
Segment Reporting, Measurement for Transactions Between Reportable Segments									2511	2255	2350
Interest expense (income)									1,542	1,237	1,233
Other income, net									1,110	690	784
Income (loss) before income taxes									669	4,744	2,216
Identifiable assets	102,282				89,939				102,282	89,939
Capital expenditures									6,119	6,563	5,043
Acquisition of businesses, net of cash acquired and investments in affiliates									0	4,103	10,683
Depreciation and amortization									4,330	3,070	2,117
Retail
Segment Reporting Information [Line Items]
Sales and merchandising revenues									140,807	140,706	150,964
Interest expense (income)									666	689	776
Other income, net									955	501	554
Income (loss) before income taxes									(620)	(7,534)	(3,951)
Identifiable assets	44,536				44,910				44,536	44,910
Capital expenditures									1,190	2,944	2,794
Depreciation and amortization									2,668	3,119	3,002
Other Segments
Segment Reporting Information [Line Items]
Interest expense (income)									(471)	(527)	(426)
Other income, net									1,031	2,407	1,733
Income (loss) before income taxes									(34,505)	(20,925)	(16,189)
Identifiable assets	186,287				406,104				186,287	406,104
Capital expenditures									8,448	3,463	7,102
Acquisition of businesses, net of cash acquired and investments in affiliates									100	1,050	0
Depreciation and amortization									4,204	1,415	1,358
Noncontrolling interests
Segment Reporting Information [Line Items]
Income (loss) before income taxes									$ 12,919	$ 5,763	$ (3,915)