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Derivatives (Details) In Billions, unless otherwise specified	Jun. 30, 2013 USD ($)	Jun. 30, 2013 JPY (¥)	Dec. 31, 2012 USD ($)	Dec. 31, 2012 JPY (¥)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Total guarantee value	$ 2.2	¥ 222.2	$ 2.7	¥ 230.0
Collective account values of underlying variable annuities as a percentage of the guarantee value	96.00%	96.00%	87.00%	87.00%

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- Definition

Represents the collective account values of underlying variable annuities as a percentage of the guarantee value of the associated variable annuity reinsurance liability.

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No definition available.

+ Details

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- Definition

Total notional account value guaranteed with certain variable annuities.

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No definition available.

+ Details

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