Inventories (Details) $ in Thousands, bu in Millions	Dec. 31, 2017 USD ($) bu	Dec. 31, 2016 USD ($) bu
Inventory, Net [Abstract]
Grain	$ 505,217	$ 495,139
Ethanol and coproducts	11,003	10,887
Plant nutrients and cob products	126,962	150,259
Retail merchandise	0	20,678
Railcar repair parts	5,521	5,784
Total inventories	$ 648,703	$ 682,747
Grain held in storage and excluded from inventory calculations (bushels) | bu	1.0	0.9