Notes Payable and Long-Term Debt - Footnote Narrative (Details) (USD $)	May 31, 2013	Aug. 31, 2012	May 31, 2012
Debt Instrument [Line Items]
Notes payable	$ 872,138,000	$ 803,622,000	$ 621,921,000
Notes payable | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Notes payable	432,892,000	269,783,000	201,613,000
Three-year revolving facilities | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	1,250,000,000
Three-year and five-year revolving facilities | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	2,500,000,000
Line of Credit Facility, Amount Outstanding	0	0	0
Five-Year Revolving Facilities [Member] | Line of credit | Revolving credit facility
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	2,500,000,000
CHS Capital notes payable | Notes payable, other payables
Debt Instrument [Line Items]
Notes payable	439,246,000	533,839,000	420,308,000
Private placement, Accredited Investors [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000,000
Private placement, payable in its entirety in 2033 [Domain] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.71%