Fair Value Measurements - Fair Value Reconciliation Liabilities Using Significant Unobservable Inputs (Level 3) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended	3 Months Ended
Aug. 31, 2012 Accrued liability for contingent crack spread payments related to purchase of noncontroling interests	Aug. 31, 2012 Accrued liability for contingent crack spread payments related to purchase of noncontroling interests Cost of Goods, Total	Aug. 31, 2012 Mandatorily redeemable noncontrolling interests	Aug. 31, 2012 Mandatorily redeemable noncontrolling interests Net Interest
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balances, September 1, 2011	$ 0		$ 0
Purchases	105,188		328,676
Total gains included in cost of goods sold and net interest		22,328		(6,031)
Balances, August 31, 2012	$ 127,516		$ 334,707

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Amount of gain (loss) recognized in earnings, arising from liabilities measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Purchases that have taken place during the period in relation to liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

This element represents a liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

+ Details

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