Exit Costs and Assets Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Assets held for sale		$ 392	$ 37,859
Disposal Group, Held-for-sale, Not Discontinued Operations
Restructuring Cost and Reserve [Line Items]
Assets held for sale		400	37,900
Disposal Group, Held-for-sale, Not Discontinued Operations | Grain Group | TENNESSEE
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment, held for sale			19,500
Inventories, held for sale			11,400
Commodity derivative asset, held for sale			1,200
Disposal Group, Held-for-sale, Not Discontinued Operations | Retail Store
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment, held for sale			4,200
Disposal Group, Held-for-sale, Not Discontinued Operations | Plant Nutrient Group
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment, held for sale			$ 1,600
Disposal Group, Held-for-sale, Not Discontinued Operations | Administrative Offices
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment, held for sale		$ 200
Discontinued Operations, Disposed of by Means Other than Sale | Retail Business
Restructuring Cost and Reserve [Line Items]
Business exit costs	$ 11,500