| **Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) (USD $)In Millions, unless otherwise specified** | Mar. 31, 2012 | Dec. 31, 2011 |
|----------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Total fixed maturity securities                                                                                                              | $ 40,837      | $ 39,937      |
| Equity securities                                                                                                                            | 298           | 304           |
| Short term investments                                                                                                                       | 1,638         | 1,641         |
| Separate account business                                                                                                                    | 402           | 417           |
| Derivative financial instruments, included in Other liabilities                                                                              | (2)           | (1)           |
| Fair Value, Measurements, Recurring [Member]                                                                                                 |          |          |
| Total fixed maturity securities                                                                                                              | 40,837        | 39,937        |
| Equity securities                                                                                                                            | 298           | 304           |
| Derivative and other financial instruments, included in Other invested assets                                                                | 11            | 12            |
| Short term investments                                                                                                                       | 1,380         | 1,641         |
| Life settlement contracts, included in Other assets                                                                                          | 115           | 117           |
| Separate account business                                                                                                                    | 402           | 417           |
| Total assets                                                                                                                                 | 43,043        | 42,428        |
| Derivative financial instruments, included in Other liabilities                                                                              | (2)           | (1)           |
| Total liabilities                                                                                                                            | (2)           | (1)           |
| Fair Value, Measurements, Recurring [Member] | Corporate and other bonds [Member]                                                            |          |          |
| Total fixed maturity securities                                                                                                              | 21,288        | 20,884        |
| Fair Value, Measurements, Recurring [Member] | States, municipalities and political subdivisions [Member]                                    |          |          |
| Total fixed maturity securities                                                                                                              | 10,183        | 9,782         |
| Fair Value, Measurements, Recurring [Member] | Total asset-backed [Member]                                                                   |          |          |
| Total fixed maturity securities                                                                                                              | 8,362         | 8,084         |
| Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed [Member]                                                          |          |          |
| Total fixed maturity securities                                                                                                              | 5,994         | 5,775         |
| Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed [Member]                                                           |          |          |
| Total fixed maturity securities                                                                                                              | 1,329         | 1,354         |
| Fair Value, Measurements, Recurring [Member] | Other asset-backed [Member]                                                                   |          |          |
| Total fixed maturity securities                                                                                                              | 1,039         | 955           |
| Fair Value, Measurements, Recurring [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]                    |          |          |
| Total fixed maturity securities                                                                                                              | 236           | 493           |
| Fair Value, Measurements, Recurring [Member] | Foreign government [Member]                                                                   |          |          |
| Total fixed maturity securities                                                                                                              | 655           | 636           |
| Fair Value, Measurements, Recurring [Member] | Redeemable preferred stock [Member]                                                           |          |          |
| Total fixed maturity securities                                                                                                              | 113           | 58            |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member]                                                                              |          |          |
| Total fixed maturity securities                                                                                                              | 323           | 548           |
| Equity securities                                                                                                                            | 115           | 124           |
| Derivative and other financial instruments, included in Other invested assets                                                                |     |     |
| Short term investments                                                                                                                       | 797           | 1,106         |
| Life settlement contracts, included in Other assets                                                                                          |     |     |
| Separate account business                                                                                                                    | 5             | 21            |
| Total assets                                                                                                                                 | 1,240         | 1,799         |
| Derivative financial instruments, included in Other liabilities                                                                              |     |     |
| Total liabilities                                                                                                                            |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate and other bonds [Member]                                         |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | States, municipalities and political subdivisions [Member]                 |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Total asset-backed [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Residential mortgage-backed [Member]                                       |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial mortgage-backed [Member]                                        |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other asset-backed [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member] |          |          |
| Total fixed maturity securities                                                                                                              | 194           | 451           |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign government [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              | 124           | 92            |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Redeemable preferred stock [Member]                                        |          |          |
| Total fixed maturity securities                                                                                                              | 5             | 5             |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member]                                                                              |          |          |
| Total fixed maturity securities                                                                                                              | 38,866        | 37,882        |
| Equity securities                                                                                                                            | 109           | 113           |
| Derivative and other financial instruments, included in Other invested assets                                                                |     | 1             |
| Short term investments                                                                                                                       | 583           | 508           |
| Life settlement contracts, included in Other assets                                                                                          |     |     |
| Separate account business                                                                                                                    | 393           | 373           |
| Total assets                                                                                                                                 | 39,951        | 38,877        |
| Derivative financial instruments, included in Other liabilities                                                                              | (1)           |     |
| Total liabilities                                                                                                                            | (1)           |     |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate and other bonds [Member]                                         |          |          |
| Total fixed maturity securities                                                                                                              | 20,802        | 20,402        |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | States, municipalities and political subdivisions [Member]                 |          |          |
| Total fixed maturity securities                                                                                                              | 10,010        | 9,611         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Total asset-backed [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              | 7,426         | 7,230         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed [Member]                                       |          |          |
| Total fixed maturity securities                                                                                                              | 5,547         | 5,323         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial mortgage-backed [Member]                                        |          |          |
| Total fixed maturity securities                                                                                                              | 1,224         | 1,295         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other asset-backed [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              | 655           | 612           |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member] |          |          |
| Total fixed maturity securities                                                                                                              | 42            | 42            |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign government [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              | 531           | 544           |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Redeemable preferred stock [Member]                                        |          |          |
| Total fixed maturity securities                                                                                                              | 55            | 53            |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member]                                                                              |          |          |
| Total fixed maturity securities                                                                                                              | 1,648         | 1,507         |
| Equity securities                                                                                                                            | 74            | 67            |
| Derivative and other financial instruments, included in Other invested assets                                                                | 11            | 11            |
| Short term investments                                                                                                                       |     | 27            |
| Life settlement contracts, included in Other assets                                                                                          | 115           | 117           |
| Separate account business                                                                                                                    | 4             | 23            |
| Total assets                                                                                                                                 | 1,852         | 1,752         |
| Derivative financial instruments, included in Other liabilities                                                                              | (1)           | (1)           |
| Total liabilities                                                                                                                            | (1)           | (1)           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate and other bonds [Member]                                         |          |          |
| Total fixed maturity securities                                                                                                              | 486           | 482           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | States, municipalities and political subdivisions [Member]                 |          |          |
| Total fixed maturity securities                                                                                                              | 173           | 171           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Total asset-backed [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              | 936           | 854           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Residential mortgage-backed [Member]                                       |          |          |
| Total fixed maturity securities                                                                                                              | 447           | 452           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial mortgage-backed [Member]                                        |          |          |
| Total fixed maturity securities                                                                                                              | 105           | 59            |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other asset-backed [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              | 384           | 343           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member] |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign government [Member]                                                |          |          |
| Total fixed maturity securities                                                                                                              |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Redeemable preferred stock [Member]                                        |          |          |
| Total fixed maturity securities                                                                                                              | $ 53          |     |

| X                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Life settlement contracts, included in Other assets
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.
+ References
No definition available.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value as of the balance sheet date of the gross assets less the gross liabilities of a derivative asset or group of derivative assets.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph a -Clause 1 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the aggregate of the liabilities reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
For an unclassified balance sheet, this item represents investments in common and preferred stocks and other forms of securities that provide ownership interests in a corporation.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
For an unclassified balance sheet, this item represents investments in debt securities having predetermined or determinable maturity dates.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The fair value of the assets held by the Entity for the benefit of separate account policyholders.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 7 -Section 03 -Paragraph 11Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 80 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6484091&loc=d3e19268-158472Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 9Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Separate Account -URI http://asc.fasb.org/extlink&oid=6524887 -Topic 944Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 03-1 -Paragraph 10-18 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 53, 54 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.
+ References
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