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	Nov. 30, 2017 T rail_car t Bushels MMBtu Barrels	Aug. 31, 2017 T rail_car t Bushels MMBtu Barrels
Grain and oilseed - bushels | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	588,263	570,673
Grain and oilseed - bushels | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	805,041	768,540
Energy products - barrels | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	16,254	15,072
Energy products - barrels | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	19,300	18,252
Processed grain and oilseed - tons | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	196	299
Processed grain and oilseed - tons | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	1,700	2,347
Crop nutrients - tons | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	25	9
Crop nutrients - tons | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	4	15
Ocean and barge freight - metric tons | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | t	4,785	2,777
Ocean and barge freight - metric tons | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | t	3,144	1,766
Rail freight - rail cars | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | rail_car	151	176
Rail freight - rail cars | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | rail_car	68	75
Natural gas - MMBtu | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	1,500	500
Natural gas - MMBtu | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	0	0