Summary of Significant Accounting Policies - Narrative (Details) (USD $)	12 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
Equity
Preferred stock, dividend rate, percentage	8.00%
Derivative Instrument Detail
Notional Amount of Interest Rate Cash Flow Hedge Derivatives	$ 300,000,000
Debt, Weighted Average Interest Rate	5.00%
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Assets at Fair Value	7,100,000
Finite-Lived Intangible Assets, Net
Number of Refineries	2
Income Taxes [Abstract]
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value	5,900,000
Interest Rate Contracts, Expiring At Various Times Through Fiscal 2018
Derivative Instrument Detail
Notional Amount of Interest Rate Cash Flow Hedge Derivatives	8,600,000
Interest Rate Contracts, Expiring During Fiscal 2013
Derivative Instrument Detail
Notional Amount of Interest Rate Cash Flow Hedge Derivatives	300,000
Minimum | Subsidiaries
Income Taxes [Abstract]
Subsidiaries Ownership Percentage	80.00%
Minimum | Customer Lists, Trademarks and Agreements Not to Compete
Finite-Lived Intangible Assets, Net
Finite-Lived Intangible Asset, Useful Life	2 years
Minimum | Major Maintenace Activities Requiring Shutdown
Finite-Lived Intangible Assets, Net
Finite-Lived Intangible Asset, Useful Life	2 years
Minimum | Land Improvements [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	P15Y
Minimum | Building
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	20
Minimum | Machinery, Equipment, Office and Other
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	P5Y
Minimum | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	3
Maximum
Derivative Instrument Detail
Notes Payable Maturities	30 days
Maximum | Customer Lists, Trademarks and Agreements Not to Compete
Finite-Lived Intangible Assets, Net
Finite-Lived Intangible Asset, Useful Life	30 years
Maximum | Major Maintenace Activities Requiring Shutdown
Finite-Lived Intangible Assets, Net
Finite-Lived Intangible Asset, Useful Life	4 years
Maximum | Land Improvements [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	P20Y
Maximum | Land Improvements and Buildings
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	40
Maximum | Machinery, Equipment, Office and Other
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	P20Y
Maximum | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	10
Service Life
Property, Plant and Equipment
Property, Plant and Equipment, Estimated Useful Lives	P20Y	P16Y
Change in Accounting Estimate, Financial Effect		27,000,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative Instrument Detail
Derivative Assets	24,135,000
Immaterial Balance Sheet Revision [Member] | Derivative Financial Instruments, Assets [Member]
Income Taxes [Abstract]
Quantifying Misstatement in Current Year Financial Statements, Amount	221,900,000
Immaterial Balance Sheet Revision [Member] | Derivative Financial Instruments, Liabilities [Member]
Income Taxes [Abstract]
Quantifying Misstatement in Current Year Financial Statements, Amount	340,800,000
Immaterial Balance Sheet Revision [Member] | Accounts Payable [Member]
Income Taxes [Abstract]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 118,900,000