Inventories (Details) $ in Thousands, bu in Millions	Mar. 31, 2017 USD ($) bu	Dec. 31, 2016 USD ($) bu	Mar. 31, 2016 USD ($) bu
Inventory, Net [Abstract]
Grain	$ 443,870	$ 495,139	$ 450,414
Ethanol and co-products	15,549	10,887	11,895
Plant nutrients and cob products	165,584	150,259	207,109
Retail merchandise	11,082	20,678	27,792
Railcar repair parts	5,209	5,784	6,185
Other	0	0	57
Total inventories	$ 641,294	$ 682,747	$ 703,452
Bushels of grain held in storage and excluded from inventory calculations | bu	2.7	0.9	2.8