Derivative Financial Instruments and Hedging Activities - Fair Value of Commodity Derivative Instruments (Details) - USD ($) $ in Thousands	May 31, 2019	Aug. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 281,878	$ 352,029
Derivative Liabilities	$ 308,087	$ 445,755

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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