Fair Value Measurements - Fair Value Measurements (Details) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Nov. 30, 2012	Aug. 31, 2012	Nov. 30, 2011
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventory, Current, Fair Value Disclosure
Foreign Currency Contract, Asset, Fair Value Disclosure	2,826	957
Other assets	75,873	75,000	69,271
Total assets	125,953	146,543	217,186
Foreign currency derivatives	2,077	2,366
Accrued liability for contingent crack spread payments related to purchase of noncontrolling interest
Total liabilities	19,383	152,415	18,583
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodity and feight derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity and freight derivatives, assets	47,254	70,586	147,915
Derivative liabilities	17,306	150,049	18,583
Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate swap derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventory, Current, Fair Value Disclosure	2,186,328	1,702,757	1,423,083
Foreign Currency Contract, Asset, Fair Value Disclosure
Other assets
Total assets	2,527,715	2,481,119	1,677,489
Foreign currency derivatives
Accrued liability for contingent crack spread payments related to purchase of noncontrolling interest
Total liabilities	261,493	356,590	282,854
Significant Other Observable Inputs (Level 2) | Commodity and feight derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity and freight derivatives, assets	341,387	778,362	254,406
Derivative liabilities	261,010	356,046	282,259
Significant Other Observable Inputs (Level 2) | Interest rate swap derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	483	544	595
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventory, Current, Fair Value Disclosure
Foreign Currency Contract, Asset, Fair Value Disclosure
Other assets
Total assets
Foreign currency derivatives
Accrued liability for contingent crack spread payments related to purchase of noncontrolling interest	170,621	127,516	105,188
Total liabilities	170,621	127,516	105,188
Significant Unobservable Inputs (Level 3) | Commodity and feight derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity and freight derivatives, assets
Derivative liabilities
Significant Unobservable Inputs (Level 3) | Interest rate swap derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventory, Current, Fair Value Disclosure	2,186,328	1,702,757	1,423,083
Foreign Currency Contract, Asset, Fair Value Disclosure	2,826	957
Other assets	75,873	75,000	69,271
Total assets	2,653,668	2,627,662	1,894,675
Foreign currency derivatives	2,077	2,366
Accrued liability for contingent crack spread payments related to purchase of noncontrolling interest	170,621	127,516	105,188
Total liabilities	451,497	636,521	406,625
Estimate of Fair Value, Fair Value Disclosure [Member] | Commodity and feight derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity and freight derivatives, assets	388,641	848,948	402,321
Derivative liabilities	278,316	506,095	300,842
Estimate of Fair Value, Fair Value Disclosure [Member] | Interest rate swap derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 483	$ 544	$ 595