Inventories (Details) $ in Thousands, bu in Millions	Sep. 30, 2015 USD ($) bu	Dec. 31, 2014 USD ($) bu	Sep. 30, 2014 USD ($) bu
Inventory, Net [Abstract]
Grain	$ 325,536	$ 570,916	$ 227,014
Ethanol and by-products	8,365	13,154	9,696
Plant nutrients and cob products	161,562	181,136	128,573
Retail merchandise	26,079	23,810	25,647
Railcar repair parts	6,057	6,431	5,336
Other	190	208	198
Total inventories	$ 527,789	$ 795,655	$ 396,464
Bushels of grain held in storage and excluded from inventory calculations | bu	3.2	3.1	2.0