Derivative Financial Instruments - Counterparty Credit Quality with Respect to Fair Value of OTC Derivatives Assets (Detail) $ in Thousands	Aug. 31, 2017 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
A- or higher	$ 136,201
BBB- to BBB	50,742
BB or lower	72,249
Unrated	57,745
Total OTC derivative assets included in Financial instruments owned	$ 316,937

Fair value of OTC derivatives assets, counterparty credit quality BB or lower.

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Fair value of OTC derivatives assets, counterparty credit quality BBB- to BBB.

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Fair value of OTC derivatives assets, counterparty credit quality unrated.

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Fair Value Of Over Counter Derivatives Assets Counterparty Credit QualityA Or Higher

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OTC Derivative Assets Included In Financial Instruments Owned.

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