Notes Payable and Long-Term Debt - Schedule of short-term debt (Details) - USD ($) $ in Thousands	Aug. 31, 2017	Aug. 31, 2016
Short-term Debt [Line Items]
Notes payable	$ 1,988,215	$ 2,731,479
CHS Capital notes payable | CHS Capital notes payable
Short-term Debt [Line Items]
Notes payable	292,792	928,305
Notes Payable, Other Payables [Member] | Recourse loan commitments
Short-term Debt [Line Items]
Notes payable	144,100
Short-term bank loans and notes payable current borrowing capacity	220,200
Notes Payable, Other Payables [Member] | Short-Term Notes Payable, Surplus Funds Program [Member]
Short-term Debt [Line Items]
Notes payable	119,300
Revolving credit facility | Line of credit | Three-Year Revolving Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity	325,000
Line of Credit Facility, Fair Value of Amount Outstanding	250,000
Revolving credit facility | Notes Payable, Other Payables [Member] | Notes Payable, Other Payables [Member]
Short-term Debt [Line Items]
Notes payable	$ 1,695,423	$ 1,803,174