Summary of Significant Accounting Policies - Purchase and Sales Contracts Outstanding (Details)	Aug. 31, 2013 Bushels T Barrels	Aug. 31, 2012 T Bushels Barrels
Sales Contracts
Derivative [Line Items]
Grain and oilseed - bushels	806,295,000	1,074,535,000
Energy products - barrels	21,312,000	19,561,000
Soy products - tons	847,000	215,000
Crop nutrients - tons	1,050,000	725,000
Ocean and barge freight - metric tons	151,000	183,000
Derivative, Number of Units, Cargo and Freight Rail Contract	43,000	34,000
Derivative, Number of Units, Livestock	17,280,000	3,440,000
Purchase Contracts
Derivative [Line Items]
Grain and oilseed - bushels	521,979,000	722,895,000
Energy products - barrels	12,626,000	9,047,000
Soy products - tons	24,000	15,000
Crop nutrients - tons	968,000	600,000
Ocean and barge freight - metric tons	1,225,000	1,018,000
Derivative, Number of Units, Cargo and Freight Rail Contract	220,000	184,000
Derivative, Number of Units, Livestock		2,560,000