Derivative Financial Instruments - Counterparty Credit Quality with Respect to Fair Value of OTC Derivatives Assets (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value of OTC derivatives assets, Counterparty credit quality, A- or higher	$ 508,060
Fair value of OTC derivatives assets, Counterparty credit quality, BBB- to BBB+	107,645
Fair value of OTC derivatives assets, Counterparty credit quality, BB+ or lower	94,772
Fair value of OTC derivatives assets, Counterparty credit quality, Unrated	95,674
Total OTC derivative assets included in Financial instruments owned	$ 806,151

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

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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 BB or lower.

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

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OTC Derivative Assets Included In Financial Instruments Owned.

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