Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) $ in Thousands	3 Months Ended	9 Months Ended
	May. 31, 2015 USD ($) Refineries	May. 31, 2015 USD ($) Refineries	May. 31, 2014 USD ($)
Finite-Lived Intangible Assets [Line Items]
Number of Refineries | Refineries	2	2
Expenditures for Major Repairs		$ 145,550	$ 0
Capitalized Maintenance Expense, Deferred During the Period	$ 137,300	$ 145,600	$ 0
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