Acquisitions - National Cooperative Refinery Association Acquisition (Details) $ in Thousands	3 Months Ended		12 Months Ended			37 Months Ended	46 Months Ended
	Nov. 30, 2014 USD ($)	Nov. 30, 2013 USD ($)	Aug. 31, 2015 USD ($)	Aug. 31, 2014 USD ($)	Aug. 31, 2013 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Nov. 29, 2011 USD ($) Closings contingent_payments
Business Acquisition [Line Items]
Current portion of mandatorily redeemable noncontrolling interest			$ 152,607	$ 65,981
National Cooperative Refinery Association
Business Acquisition [Line Items]
Percentage of voting interest acquired								25.60%
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage			88.90%					74.40%
National Cooperative Refinery Association | Accounts Payable and Accrued Liabilities [Member]
Business Acquisition [Line Items]
Accrued liability for contingent crack spread payments related to purchase of noncontrolling interest			$ 2,600
National Cooperative Refinery Association | Accrued liability for contingent crack spread payments related to purchase of noncontroling interests
Business Acquisition [Line Items]
Accrued liability for contingent crack spread payments related to purchase of noncontrolling interest			76,000	114,900
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			(36,300)	(19,200)
National Cooperative Refinery Association | Interest, Net
Business Acquisition [Line Items]
Patronage earned by member			$ 31,000	$ 65,500	$ 142,400
National Cooperative Refinery Association | Growmark
Business Acquisition [Line Items]
Percentage of voting interest acquired								18.60%
Number of separate closings | Closings								4
Business Combination, Step Acquisition, Future Payments Due, First Three Closings								$ 48,000
Aggregate base purchase price, amount paid at the final closing								$ 111,400
Number of purchase price payments | contingent_payments								2
National Cooperative Refinery Association | MFA
Business Acquisition [Line Items]
Percentage of voting interest acquired								7.00%
Number of separate closings | Closings								4
Business Combination, Step Acquisition, Future Payments Due, First Three Closings								$ 18,000
Aggregate base purchase price, amount paid at the final closing								$ 41,600
Number of purchase price payments | contingent_payments								2
Crack Spread Contingent Payment [Member]
Business Acquisition [Line Items]
Business Acquisition, Contingent Consideration, Potential Cash Payment	$ 0	$ 16,500
Subsequent Event [Member] | National Cooperative Refinery Association
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage						100.00%	100.00%
Subsequent Event [Member] | National Cooperative Refinery Association | Growmark
Business Acquisition [Line Items]
Aggregate base purchase price						$ 255,500
Subsequent Event [Member] | National Cooperative Refinery Association | MFA
Business Acquisition [Line Items]
Aggregate base purchase price							$ 95,500