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, 2019 T t Bushels MMBtu Barrels	Aug. 31, 2018 T t Bushels MMBtu Barrels
Grain and oilseed contracts [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	547,096	715,866
Grain and oilseed contracts [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	717,522	929,873
Energy products [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	13,895	17,011
Energy products [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	4,663	8,329
Processed grain and oilseed contracts [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	597	1,064
Processed grain and oilseed contracts [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	2,454	2,875
Crop nutrient contracts | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	76	11
Crop nutrient contracts | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	23	76
Ocean freight contracts | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | t	295	227
Ocean freight contracts | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | t	85	45
Natural gas contracts [Member] | Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	130	610
Natural gas contracts [Member] | Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	0	0