Invested Assets (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Tax exempt, Amortized Cost	$ 18,779	$ 18,786
Tax exempt, Gross Unrealized Appreciation	1,509	1,462
Tax exempt, Gross Unrealized Depreciation	28	37
Tax exempt, Fair Value	20,260	20,211
Taxable, Amortized Cost	16,196	15,976
Taxable, Gross Unrealized Appreciation	1,073	1,033
Taxable, Gross Unrealized Depreciation	16	36
Taxable, Fair Value	17,253	16,973
Total fixed maturities, Amortized Cost	34,975	34,762
Total fixed maturities, Gross Unrealized Appreciation	2,582	2,495
Total fixed maturities, Gross Unrealized Depreciation	44	73
Total fixed maturities, Fair Value	37,513	37,184
Equity Securities, Amortized Cost	1,261	1,264
Equity securities, Gross Unrealized Appreciation	362	319
Equity securities, Gross Unrealized Depreciation	40	71
Equity securities, Fair Value	1,583	1,512
U.S. Government and government agency and authority obligations [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized Cost	1,006	813
Taxable, Gross Unrealized Appreciation	71	57
Taxable, Gross Unrealized Depreciation	1	2
Taxable, Fair Value	1,076	868
Corporate bonds [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized Cost	6,591	6,049
Taxable, Gross Unrealized Appreciation	503	440
Taxable, Gross Unrealized Depreciation	10	24
Taxable, Fair Value	7,084	6,465
Foreign government and government agency obligations [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized Cost	6,276	6,409
Taxable, Gross Unrealized Appreciation	385	416
Taxable, Gross Unrealized Depreciation	1	2
Taxable, Fair Value	6,660	6,823
Residential mortgage-backed securities [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized Cost	579	821
Taxable, Gross Unrealized Appreciation	34	41
Taxable, Gross Unrealized Depreciation	3	7
Taxable, Fair Value	610	855
Commercial mortgage-backed securities [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized Cost	1,744	1,884
Taxable, Gross Unrealized Appreciation	80	79
Taxable, Gross Unrealized Depreciation	1	1
Taxable, Fair Value	$ 1,823	$ 1,962

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The excess of the fair value of equity securities over its amortized cost which excess value has not been recognized in earnings of the entity.

+ References

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The excess of amortized cost of equity securities over its fair value which deficiency has not been recognized in earnings of the entity.

+ References

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The excess of the fair value of fixed maturities over its amortized cost which excess value has not been recognized in earnings of the entity.

+ References

No definition available.

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The excess of amortized cost of fixed maturities over its fair value which deficiency has not been recognized in earnings of the entity.

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This item represents total taxable debt securities that are categorized as neither held-to-maturity nor trading. Such securities are reported at fair value; unrealized gains and losses of such securities are excluded from earnings and included in other comprehensive income.

+ References

No definition available.

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This item represents the amortized cost basis of taxable debt securities that are categorized as neither held-to-maturity nor trading.

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No definition available.

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The excess of the fair value of taxable fixed maturities over its amortized cost which excess value has not been recognized in earnings of the entity.

+ References

No definition available.

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The excess of amortized cost of taxable fixed maturities over its fair value which deficiency has not been recognized in earnings of the entity.

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This item represents total tax-exempt debt securities that are categorized as neither held-to-maturity nor trading. Such securities are reported at fair value; unrealized gains and losses of such securities are excluded from earnings and included in other comprehensive income.

+ References

No definition available.

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This item represents the amortized cost basis of tax exempt debt securities that are categorized as neither held-to-maturity nor trading.

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The excess of the fair value of tax exempt fixed maturities over its amortized cost which excess value has not been recognized in earnings of the entity.

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No definition available.

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The excess of amortized cost of tax exempt fixed maturities over its fair value which deficiency has not been recognized in earnings of the entity.

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This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This item represents the cost of equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments for other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Amount of equity securities categorized neither as held-to-maturity nor as trading.

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