Fair Value Measurements - Fair Value Reconciliation Liabilities Using Significant Unobservable Inputs (3 month) (Level 3) (Details) (Accrued liability for contingent crack spread payments related to purchase of noncontroling interests, USD $) In Thousands, unless otherwise specified	9 Months Ended					3 Months Ended		9 Months Ended
	May 31, 2012	May 31, 2013	Nov. 30, 2012	Aug. 31, 2012	Nov. 30, 2011	May 31, 2013 Cost of Goods, Total	May 31, 2012 Cost of Goods, Total	May 31, 2013 Cost of Goods, Total	May 31, 2012 Cost of Goods, Total
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	$ 105,188
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance	0	146,245	140,987	127,516	101,003
Total gains or losses included in cost of goods sold and net interest						5,258	(2,556)	18,729	(6,741)
Balance	$ 98,447	$ 146,245	$ 140,987	$ 127,516	$ 101,003