Derivative Financial Instruments and Hedging Activities Purchase and Sale Contracts (Details) - Not Designated as Hedging Instrument [Member] t in Thousands, rail_car in Thousands, T in Thousands, MMBtu in Thousands, Bushels in Thousands, Barrels in Thousands	Feb. 28, 2018 rail_car T t Bushels MMBtu Barrels	Aug. 31, 2017 rail_car T t Bushels MMBtu Barrels
Grain and oilseed - bushels | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	777,266	570,673
Grain and oilseed - bushels | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	1,037,549	768,540
Energy products - barrels | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	20,648	15,072
Energy products - barrels | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	11,277	18,252
Processed grain and oilseed - tons | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	238	299
Processed grain and oilseed - tons | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	1,158	2,347
Crop nutrients - tons | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	15	9
Crop nutrients - tons | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	9	15
Ocean and barge freight - metric tons | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | t	6,263	2,777
Ocean and barge freight - metric tons | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | t	3,349	1,766
Rail freight - rail cars | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | rail_car	168	176
Rail freight - rail cars | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | rail_car	53	75
Natural gas - MMBtu | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	300	500
Natural gas - MMBtu | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	0	0