Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]
Sales and merchandising revenues	$ 952,927		$ 1,181,374		$ 3,268,303		$ 4,020,308
Inter-segment sales	4,796		4,868		19,545		18,475
Interest expense	4,253		5,348		16,401		16,607
Equity in earnings of affiliates, net	23,917		22,177		76,631		39,991
Other income (expense), net	1,685		7,605		25,094		11,623
Income (loss) before income taxes	29,530		28,387		144,515		97,990
Identifiable assets	2,082,992		1,882,291		2,082,992		1,882,291		2,273,556
Grain
Segment Reporting Information [Line Items]
Sales and merchandising revenues	575,354		765,833		1,814,517		2,493,678
Inter-segment sales	894		0		4,256		333
Interest expense	1,723		1,391		7,203		7,714
Equity in earnings of affiliates, net	10,190		12,003		20,541		24,940
Other income (expense), net	(2,354)	[1]	1,216	[1]	16,967	[1]	1,438	[1]
Income (loss) before income taxes	12,449		14,323		34,110		24,675
Identifiable assets	713,352		784,869		713,352		784,869		921,914
Ethanol
Segment Reporting Information [Line Items]
Sales and merchandising revenues	179,405		213,384		594,613		634,933
Interest expense	77		289		253		895
Equity in earnings of affiliates, net	13,727		10,174		56,090		15,051
Other income (expense), net	71		35		201		465
Income (loss) before income taxes	21,253		10,904		74,981		23,984
Identifiable assets	257,194		207,530		257,194		207,530		229,797
Plant Nutrient
Segment Reporting Information [Line Items]
Sales and merchandising revenues	110,809		95,681		530,334		537,922
Inter-segment sales	3,401		4,243		12,929		15,955
Interest expense	1,017		746		2,748		2,461
Other income (expense), net	2,617		320		3,193		459
Income (loss) before income taxes	(129)		(1,643)		23,464		21,035
Identifiable assets	252,675		258,772		252,675		258,772		268,238
Rail
Segment Reporting Information [Line Items]
Sales and merchandising revenues	32,022		47,523		117,733		132,488
Inter-segment sales	109		109		327		318
Interest expense	1,821		1,220		5,381		4,162
Other income (expense), net	792		5,031		2,289		6,679
Income (loss) before income taxes	4,160		12,360		25,889		36,614
Identifiable assets	316,851		294,528		316,851		294,528		312,654
Turf and Specialty
Segment Reporting Information [Line Items]
Sales and merchandising revenues	22,631		27,624		109,269		117,955
Inter-segment sales	392		516		2,033		1,869
Interest expense	338		203		1,178		951
Other income (expense), net	244		135		1,018		585
Income (loss) before income taxes	(2,885)		(83)		488		6,113
Identifiable assets	84,212		71,600		84,212		71,600		89,939
Retail
Segment Reporting Information [Line Items]
Sales and merchandising revenues	32,706		31,329		101,837		103,332
Interest expense	182		152		516		519
Other income (expense), net	418		102		720		316
Income (loss) before income taxes	(968)		(2,043)		(1,666)		(3,673)
Identifiable assets	46,108		51,465		46,108		51,465		44,910
Other
Segment Reporting Information [Line Items]
Interest expense	(905)		1,347		(878)		(95)
Other income (expense), net	(103)		766		706		1,681
Income (loss) before income taxes	(6,804)		(6,309)		(23,595)		(12,563)
Identifiable assets	412,600		213,527		412,600		213,527		406,104
Noncontrolling Interests
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ 2,454		$ 878		$ 10,844		$ 1,805

[1] Increase in the nine months ended balances is related to gain on LTG partial share redemption. See Note 8. Related Party Transactions for details of the LTG gain in the first quarter of 2014.