Derivative Financial Instruments and Hedging Activities - Purchase and Sales Contracts Outstanding (Details) - Not Designated as Hedging Instrument t in Thousands, T in Thousands, MMBtu in Thousands, Bushels in Thousands, Barrels in Thousands	Aug. 31, 2018 T t Bushels MMBtu Barrels	Aug. 31, 2017 T t Bushels MMBtu Barrels
Grain and oilseed contracts [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	715,866	569,243
Grain and oilseed contracts [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	929,873	767,110
Energy products [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	17,011	15,072
Energy products [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	8,329	18,252
Processed grain and oilseed contracts [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	1,064	299
Processed grain and oilseed contracts [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	2,875	2,347
Crop nutrient contracts | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	11	9
Crop nutrient contracts | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	76	15
Ocean freight contracts | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | t	227	160
Ocean freight contracts | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | t	45	198
Natural gas contracts [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	610	500
Natural gas contracts [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	0	0