Fair Value Measurements - Fair Value Reconciliation Liabilities Using Significant Unobservable Inputs (Level 3) (Details) (Accrued liability for contingent crack spread payments related to purchase of noncontroling interests, USD $) In Thousands, unless otherwise specified			3 Months Ended
	Nov. 30, 2012	Aug. 31, 2012	Nov. 30, 2012 Cost of Goods, Total
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance	$ 170,621	$ 127,516
Total gains or losses included in cost of goods sold and net interest			43,105
Balance	$ 170,621	$ 127,516