Fair Value Measurements (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012 Year	Sep. 30, 2012 Year
Fair Value Measurements Of Financial Instruments [Line Items]
GLB - Lapse rate - lower range	1.00%	1.00%
GLB - Lapse rate - upper range	6.00%	6.00%
GLB - Spike lapse rate - lower range	10.00%	10.00%
GLB - Spike lapse rate - upper range	30.00%	30.00%
GLB - Ultimate lapse rate	10.00%	10.00%
GLB - Length of ultimate lapse rate period, years	2	2
GLB - Adjustment factor for valuable guarantees - lower	15.00%	15.00%
GLB - Adjustment factor for valuable guarantees - upper	75.00%	75.00%
Percent of GMIB guaranteed value that are represented by clients with several years of annuitization experience	36.00%	36.00%
GLB - Maximum annuitization rate	8.00%	8.00%
GLB - First year maximum annuitization rate	13.00%	13.00%
GLB - Weighted average maximum annuitization rate - rate 1	8.00%	8.00%
GLB - Weighted average maximum annuitization rate - rate 2	12.00%	12.00%
GLB - Weighted average maximum annuitization rate - rate 3	30.00%	30.00%
Guaranteed Living Benefits, Net Income Impact From Model Refinement	$ 21	$ 21
Redemption Notice Periods Lower Range [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Notice period for redemption for alternative investments investment funds, days		5
Redemption Notice Periods Upper Range [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Notice period for redemption for alternative investments investment funds, days		120

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The low end of the range of multiplicative factors used to reduce the Base Lapse Function for policies with more valuable guarantees.

+ References

No definition available.

+ Details

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- Definition

The high end of the range of multiplicative factors used to reduce the Base Lapse Function for policies with more valuable guarantees.

+ References

No definition available.

+ Details

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- Definition

The low end of the range of the per annum lapse assumption during the surrender charge period.

+ References

No definition available.

+ Details

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- Definition

The high end of the range of the per annum lapse assumption during the surrender charge period.

+ References

No definition available.

+ Details

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- Definition

The low end of the range of the per annum lapse assumption in the year immediately following the surrender charge period.

+ References

No definition available.

+ Details

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- Definition

The high end of the range of the per annum lapse assumption in the year immediately following the surrender charge period.

+ References

No definition available.

+ Details

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- Definition

The length of the ultimate lapse rate period.

+ References

No definition available.

+ Details

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- Definition

The approximate per annum lapse assumption 3 or more years following the surrender charge period.

+ References

No definition available.

+ Details

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- Definition

The highest annual annuitization rate assumption applied after the first year a policy is eligible to annuitize using a GMIB feature, used for clients for which there are several years of annuitization experience.

+ References

No definition available.

+ Details

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- Definition

The highest annual annuitization rate assumption applied in the first year a policy is eligible to annuitize using a GMIB feature, used for clients for which there are several years of annuitization experience.

+ References

No definition available.

+ Details

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- Definition

Guaranteed Living Benefits, Net Income Impact From Model Refinement

+ References

No definition available.

+ Details

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- Definition

Rate 1 - the highest annual annuitization rate assumption applied after the first year a policy is eligible to annuitize using a GMIB feature, as used in the weighted average for clients with no currently observable relevant annuitization behavior data.

+ References

No definition available.

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- Definition

Rate 2 - the highest annual annuitization rate assumption applied after the first year a policy is eligible to annuitize using a GMIB feature, as used in the weighted average for clients with no currently observable relevant annuitization behavior data.

+ References

No definition available.

+ Details

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- Definition

Rate 3 - the highest annual annuitization rate assumption applied after the first year a policy is eligible to annuitize using a GMIB feature, as used in the weighted average for clients with no currently observable relevant annuitization behavior data.

+ References

No definition available.

+ Details

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- Definition

Notice period in days for redemption of investment funds alternative investments (employ various investment strategies such as long/short equity and arbitrage/distressed.)

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No definition available.

+ Details

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- Definition

The percentage of GMIB guaranteed value that is represented by clients with several years of annuitization experience

+ References

No definition available.

+ Details

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