Fair Value Measurements (Carrying Values And Fair Values For Financial Instruments Not Measured At Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt	$ 3,360	$ 3,358
Trust preferred securities	309	309
Total liabilities	62,989	60,381
Financial Instruments Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	8,447	9,501
Short-term debt	1,251	1,300
Long-term debt	3,360	3,358
Trust preferred securities	309	309
Total liabilities	4,920	4,967
Financial Instruments Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	8,605	9,461
Short-term debt	1,251	1,300
Long-term debt	3,823	3,690
Trust preferred securities	404	364
Total liabilities	5,478	5,354
U.S. Treasury And Agency [Member] \| Financial Instruments Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	1,078	1,105
U.S. Treasury And Agency [Member] \| Financial Instruments Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	1,126	1,127
Foreign [Member] \| Financial Instruments Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	935	1,049
Foreign [Member] \| Financial Instruments Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	930	1,013
Corporate Securities [Member] \| Financial Instruments Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	2,338	2,361
Corporate Securities [Member] \| Financial Instruments Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	2,337	2,313
Mortgage-Backed Securities [Member] \| Financial Instruments Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	2,949	3,811
Mortgage-Backed Securities [Member] \| Financial Instruments Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	3,036	3,846
States, Municipalities, And Political Subdivisions [Member] \| Financial Instruments Carrying Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	1,147	1,175
States, Municipalities, And Political Subdivisions [Member] \| Financial Instruments Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fixed Maturities Held To Maturity Not Measured At Fair Value	$ 1,176	$ 1,162

Investments classified as fixed maturities held to maturity that are not carried at fair value.

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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-Topic 942

-SubTopic 210

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-Subparagraph (SX 210.9-03.16)

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Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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-Publisher FASB

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-SubTopic 10

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-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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Total of the portions of the carrying amounts as of the balance sheet date of long-term debt, which may include notes payable, bonds payable, debentures, mortgage loans, and commercial paper, which are scheduled to be repaid within one year or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

+ References

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-Publisher SEC

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