Derivative Financial Instruments and Hedging Activities Purchase and Sale Contracts (Details) - Not Designated as Hedging Instrument [Member] - Forward Contracts [Member] t in Thousands, rail_car in Thousands, T in Thousands, MMBtu in Thousands, Bushels in Thousands, Barrels in Thousands	Feb. 29, 2016 T Barrels Bushels MMBtu rail_car t	Aug. 31, 2015 T Barrels Bushels MMBtu rail_car t
Grain and oilseed - bushels | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	572,707	711,066
Grain and oilseed - bushels | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Bushels	773,130	895,326
Energy products - barrels | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	15,990	17,238
Energy products - barrels | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | Barrels	8,665	11,676
Soy product contracts [Member] | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	725	706
Soy product contracts [Member] | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	1,995	2,741
Crop nutrients contracts [Member] | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	24	48
Crop nutrients contracts [Member] | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	12	116
Ocean and barge freight contracts [Member] | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | t	3,687	5,916
Ocean and barge freight contracts [Member] | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | t	2,159	1,962
Rail freight contracts [Member] | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | rail_car	193	297
Rail freight contracts [Member] | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | rail_car	78	122
Natural Gas [Member] | Long [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	6,740	0
Natural Gas [Member] | Short [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount | MMBtu	0	0