| **Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) (USD $)In Millions, unless otherwise specified** | Mar. 31, 2013 | Dec. 31, 2012 |
|----------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Fixed maturity securities                                                                                                                    | $ 42,799      | $ 42,633      |
| Equity securities                                                                                                                            | 201           | 249           |
| Other invested assets                                                                                                                        | 49            | 59            |
| Short term investments                                                                                                                       | 1,555         | 1,832         |
| Separate account business                                                                                                                    | 279           | 312           |
| Derivative financial instruments, included in Other liabilities                                                                              | (1)           | (3)           |
| Fair Value, Measurements, Recurring [Member]                                                                                                 |          |          |
| Fixed maturity securities                                                                                                                    | 42,799        | 42,633        |
| Equity securities                                                                                                                            | 201           | 249           |
| Other invested assets                                                                                                                        | 49            | 59            |
| Short term investments                                                                                                                       | 1,504         | 1,792         |
| Life settlement contracts, included in Other assets                                                                                          | 95            | 100           |
| Separate account business                                                                                                                    | 279           | 312           |
| Total assets                                                                                                                                 | 44,927        | 45,145        |
| Derivative financial instruments, included in Other liabilities                                                                              | (1)           | (3)           |
| Total liabilities                                                                                                                            | (1)           | (3)           |
| Fair Value, Measurements, Recurring [Member] | Corporate and other bonds [Member]                                                            |          |          |
| Fixed maturity securities                                                                                                                    | 22,354        | 22,236        |
| Fair Value, Measurements, Recurring [Member] | States, municipalities and political subdivisions [Member]                                    |          |          |
| Fixed maturity securities                                                                                                                    | 10,948        | 10,783        |
| Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed [Member]                                                          |          |          |
| Fixed maturity securities                                                                                                                    | 5,683         | 5,920         |
| Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed [Member]                                                           |          |          |
| Fixed maturity securities                                                                                                                    | 1,990         | 1,822         |
| Fair Value, Measurements, Recurring [Member] | Other asset-backed [Member]                                                                   |          |          |
| Fixed maturity securities                                                                                                                    | 955           | 952           |
| Fair Value, Measurements, Recurring [Member] | Total asset-backed [Member]                                                                   |          |          |
| Fixed maturity securities                                                                                                                    | 8,628         | 8,694         |
| Fair Value, Measurements, Recurring [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]                    |          |          |
| Fixed maturity securities                                                                                                                    | 181           | 182           |
| Fair Value, Measurements, Recurring [Member] | Foreign government [Member]                                                                   |          |          |
| Fixed maturity securities                                                                                                                    | 552           | 613           |
| Fair Value, Measurements, Recurring [Member] | Redeemable preferred stock [Member]                                                           |          |          |
| Fixed maturity securities                                                                                                                    | 136           | 125           |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member]                                                                              |          |          |
| Fixed maturity securities                                                                                                                    | 342           | 344           |
| Equity securities                                                                                                                            | 120           | 117           |
| Other invested assets                                                                                                                        |     |     |
| Short term investments                                                                                                                       | 1,102         | 987           |
| Life settlement contracts, included in Other assets                                                                                          |     |     |
| Separate account business                                                                                                                    | 11            | 4             |
| Total assets                                                                                                                                 | 1,575         | 1,452         |
| Derivative financial instruments, included in Other liabilities                                                                              |     |     |
| Total liabilities                                                                                                                            |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate and other bonds [Member]                                         |          |          |
| Fixed maturity securities                                                                                                                    | 32            | 6             |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | States, municipalities and political subdivisions [Member]                 |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Residential mortgage-backed [Member]                                       |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial mortgage-backed [Member]                                        |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other asset-backed [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Total asset-backed [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member] |          |          |
| Fixed maturity securities                                                                                                                    | 155           | 158           |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign government [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    | 104           | 140           |
| Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Redeemable preferred stock [Member]                                        |          |          |
| Fixed maturity securities                                                                                                                    | 51            | 40            |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member]                                                                              |          |          |
| Fixed maturity securities                                                                                                                    | 40,977        | 41,038        |
| Equity securities                                                                                                                            | 62            | 98            |
| Other invested assets                                                                                                                        | 49            | 58            |
| Short term investments                                                                                                                       | 397           | 799           |
| Life settlement contracts, included in Other assets                                                                                          |     |     |
| Separate account business                                                                                                                    | 266           | 306           |
| Total assets                                                                                                                                 | 41,751        | 42,299        |
| Derivative financial instruments, included in Other liabilities                                                                              |     | (2)           |
| Total liabilities                                                                                                                            |     | (2)           |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate and other bonds [Member]                                         |          |          |
| Fixed maturity securities                                                                                                                    | 22,020        | 22,011        |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | States, municipalities and political subdivisions [Member]                 |          |          |
| Fixed maturity securities                                                                                                                    | 10,819        | 10,687        |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed [Member]                                       |          |          |
| Fixed maturity securities                                                                                                                    | 5,233         | 5,507         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial mortgage-backed [Member]                                        |          |          |
| Fixed maturity securities                                                                                                                    | 1,813         | 1,693         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other asset-backed [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    | 559           | 584           |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Total asset-backed [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    | 7,605         | 7,784         |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member] |          |          |
| Fixed maturity securities                                                                                                                    | 26            | 24            |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign government [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    | 448           | 473           |
| Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Redeemable preferred stock [Member]                                        |          |          |
| Fixed maturity securities                                                                                                                    | 59            | 59            |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member]                                                                              |          |          |
| Fixed maturity securities                                                                                                                    | 1,480         | 1,251         |
| Equity securities                                                                                                                            | 19            | 34            |
| Other invested assets                                                                                                                        |     | 1             |
| Short term investments                                                                                                                       | 5             | 6             |
| Life settlement contracts, included in Other assets                                                                                          | 95            | 100           |
| Separate account business                                                                                                                    | 2             | 2             |
| Total assets                                                                                                                                 | 1,601         | 1,394         |
| 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]                                         |          |          |
| Fixed maturity securities                                                                                                                    | 302           | 219           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | States, municipalities and political subdivisions [Member]                 |          |          |
| Fixed maturity securities                                                                                                                    | 129           | 96            |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Residential mortgage-backed [Member]                                       |          |          |
| Fixed maturity securities                                                                                                                    | 450           | 413           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial mortgage-backed [Member]                                        |          |          |
| Fixed maturity securities                                                                                                                    | 177           | 129           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other asset-backed [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    | 396           | 368           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Total asset-backed [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    | 1,023         | 910           |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member] |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign government [Member]                                                |          |          |
| Fixed maturity securities                                                                                                                    |     |     |
| Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Redeemable preferred stock [Member]                                        |          |          |
| Fixed maturity securities                                                                                                                    | $ 26          | $ 26          |

| 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
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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 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.Reference 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 Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959
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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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value amount of life settlement contracts accounted for under the fair value method.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Life Settlement Contract -URI http://asc.fasb.org/extlink&oid=6516907Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 325 -SubTopic 30 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6385267&loc=d3e42732-111610Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FTB85-4-1 -Paragraph 17 -Subparagraph b -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
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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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
Other investments not otherwise specified in the taxonomy.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 12 -Article 5Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph g -Article 7
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The fair value of the assets held by the Entity for the benefit of separate account policyholders.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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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