Fair Value Measurements (Detail) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Fair value of floating rate medium term notes	$ 491.3	$ 454.8
Amortized cost of floating rate medium term notes	503.9	504.6
Investments In Structured Transactions not Carried at Fair Value	325.9	327.7
Derivative Collateral Obligation to Return Cash	$ 32.9	$ 23.0
Discount Rate For Determining Fair Value Of Deposit Liabilities	140.4	142.3

Amortized cost value of certain floating rate medium term notes supported primarily by pools of European credit with varying degrees of leverage that are included within Corporate Fixed Maturity Securities.These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.

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- Definition

The amount of the obligation to return cash collateral under master

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- Definition

Discount rate used for determining fair value of deposit liabilities.

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- Definition

Fair value of certain floating rate medium term notes supported primarily by pools of European credit with varying degrees of leverage that are included within Corporate Fixed Maturity Securities.These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.

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- Definition

The Other investments balance disclosed within the Fair Value Measurements tables exclude certain structured transactions including certain investments in project finance transactions, a payment obligation and liquidity financing provided to a structured credit vehicle as a part of a third party medium term note facility.

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