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, 2017	Aug. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - beginning	$ 15,051	$ 75,982
Balance - ending	0	15,051
Cost of Goods, Total
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains included in cost of goods sold	$ (15,051)	$ (60,931)