Derivative Financial Instruments - Counterparty Credit Quality with Respect to Fair Value of OTC Derivatives Assets (Detail) $ in Thousands	May. 31, 2015 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value of OTC derivatives assets, Counterparty credit quality, A- or higher	$ 178,941
Fair value of OTC derivatives assets, Counterparty credit quality, BBB- to BBB+	129,161
Fair value of OTC derivatives assets, Counterparty credit quality, BB+ or lower	84,507
Fair value of OTC derivatives assets, Counterparty credit quality, Unrated	105,741
Total OTC derivative assets included in Financial instruments owned	$ 498,350

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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