Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) $ in Thousands	3 Months Ended
	Nov. 30, 2015 USD ($) Refineries	Nov. 30, 2014 USD ($)	Aug. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Number of Refineries | Refineries	2
Expenditures for Major Repairs	$ 18,897	$ 1,337
Capitalized Maintenance Expense, Deferred During the Period	$ 18,900	$ 1,300
Minimum [Member] | Major Maintenance Activities Requiring Shutdown [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years
Maximum [Member] | Major Maintenance Activities Requiring Shutdown [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years
National Cooperative Refinery Association [Member]
Finite-Lived Intangible Assets [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage			88.90%