Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2016 USD ($) Refineries	May 31, 2015 USD ($)	May 31, 2016 USD ($) Refineries	May 31, 2015 USD ($)	Sep. 30, 2015	Aug. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Number of Refineries | Refineries	2		2
Expenditures for Major Repairs			$ 19,338	$ 130,302
Capitalized Maintenance Expense, Deferred During the Period	$ 200	$ 122,800	$ 19,300	$ 130,300
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
Energy [Member] | National Cooperative Refinery Association [Member]
Finite-Lived Intangible Assets [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage					100.00%	88.90%