Invested Assets and Related Income (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Tax exempt, Amortized cost	$ 18,786	$ 19,072
Tax exempt, Gross unrealized appreciation	1,462	824
Tax exempt, Gross unrealized depreciation	37	122
Tax exempt, Fair value	20,211	19,774
Taxable, Amortized cost	15,976	15,989
Taxable, Gross unrealized appreciation	1,033	806
Taxable, Gross unrealized depreciation	36	50
Taxable, Fair value	16,973	16,745
Total fixed maturities, Amortized cost	34,762	35,061
Total fixed maturities, Gross unrealized appreciation	2,495	1,630
Total fixed maturities, Gross unrealized depreciation	73	172
Total fixed maturities, Fair value	37,184	36,519
Equity securities, Cost	1,264	1,285
Equity securities, Gross unrealized appreciation	319	340
Equity securities, Gross unrealized depreciation	71	75
Equity securities, Fair value	1,512	1,550
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	813	807
Taxable, Gross unrealized appreciation	57	31
Taxable, Gross unrealized depreciation	2	9
Taxable, Fair value	868	829
Corporate bonds [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized cost	6,049	6,025
Taxable, Gross unrealized appreciation	440	405
Taxable, Gross unrealized depreciation	24	20
Taxable, Fair value	6,465	6,410
Foreign government and government agency obligations [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized cost	6,409	6,176
Taxable, Gross unrealized appreciation	416	237
Taxable, Gross unrealized depreciation	2	14
Taxable, Fair value	6,823	6,399
Residential Mortgage-Backed Securities [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized cost	821	1,293
Taxable, Gross unrealized appreciation	41	63
Taxable, Gross unrealized depreciation	7	6
Taxable, Fair value	855	1,350
Commercial Mortgage-Backed Securities [Member]
Amortized cost and fair value of fixed maturities and equity securities [Abstract]
Taxable, Amortized cost	1,884	1,688
Taxable, Gross unrealized appreciation	79	70
Taxable, Gross unrealized depreciation	1	1
Taxable, Fair value	$ 1,962	$ 1,757

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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.

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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.

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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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No definition available.

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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.

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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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No definition available.

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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.

+ References

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For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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