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, 2016	Aug. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - beginning	$ 75,982	$ 114,917
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, amount currently payable	0	(2,625)
Balance - ending	15,051	75,982
Cost of Goods, Total
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains included in cost of goods sold	$ (60,931)	$ (36,310)