Summary of Significant Accounting Policies - Purchase and Sales Contracts Outstanding (Details) (Forward Contracts [Member])	Feb. 28, 2014 Bushels	Aug. 31, 2013 Bushels	Feb. 28, 2013 Bushels
Long [Member] | Grain and oilseed - bushels
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	651,998,000	521,979,000	605,309,000
Long [Member] | Energy products - barrels
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	29,067,000	12,626,000	12,103,000
Long [Member] | Soy products - tons
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	16,000	24,000	32,000
Long [Member] | Crop nutrients - tons
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	2,067,000	968,000	1,553,000
Long [Member] | Rail freight - rail cars
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	298,000	220,000	153,000
Long [Member] | Derivative number of units livestock [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount			2,920,000
Short [Member] | Grain and oilseed - bushels
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	1,009,946,000	806,295,000	906,758,000
Short [Member] | Energy products - barrels
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	32,897,000	21,312,000	21,575,000
Short [Member] | Soy products - tons
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	784,000	847,000	333,000
Short [Member] | Crop nutrients - tons
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	2,535,000	1,050,000	125,000
Short [Member] | Rail freight - rail cars
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	157,000	43,000	41,000
Short [Member] | Derivative number of units livestock [Member]
Purchase and Sales Contracts [Line Items]
Derivative, Nonmonetary Notional Amount	10,800,000	17,280,000	2,520,000