Fair Value Measurements - Fair Value Reconciliation Liabilities Using Significant Unobservable Inputs (Level 3) (Details) - Crack Spread Contingent Payment [Member] - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - beginning	$ 114,917	$ 134,134
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	(2,625)	0
Balance - ending	75,982	114,917
Cost of Goods, Total
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains included in cost of goods sold	$ (36,310)	$ (19,217)