| **Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|
||
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | $ 1,393        | $ 1,751 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | (4)            | 11 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 9              | 7 |
| Purchases                                                                                                                                                                                                      | 465            | 411 |
| Sales                                                                                                                                                                                                          | (165)          | (183) |
| Settlements                                                                                                                                                                                                    | (65)           | (95) |
| Transfers into Level 3                                                                                                                                                                                         | 26             | 33 |
| Transfers out of Level 3                                                                                                                                                                                       | (59)           | (84) |
| Balance, Ending, Assets                                                                                                                                                                                        | 1,600          | 1,851 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         | (16)           | (3) |
| Corporate and other bonds [Member]                                                                                                                                                                             |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 219            | 482 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  |      | 3 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 2              | 4 |
| Purchases                                                                                                                                                                                                      | 110            | 79 |
| Sales                                                                                                                                                                                                          | (17)           | (86) |
| Settlements                                                                                                                                                                                                    | (20)           | (19) |
| Transfers into Level 3                                                                                                                                                                                         | 26             | 33 |
| Transfers out of Level 3                                                                                                                                                                                       | (18)           | (10) |
| Balance, Ending, Assets                                                                                                                                                                                        | 302            | 486 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         | (1)            |    |
| States, municipalities and political subdivisions [Member]                                                                                                                                                     |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 96             | 171 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | (3)            |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      | 2 |
| Purchases                                                                                                                                                                                                      | 85             |    |
| Sales                                                                                                                                                                                                          | (47)           |    |
| Settlements                                                                                                                                                                                                    | (2)            |    |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 129            | 173 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Residential mortgage-backed [Member]                                                                                                                                                                           |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 413            | 452 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | 3              | 1 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      | (4) |
| Purchases                                                                                                                                                                                                      | 61             | 38 |
| Sales                                                                                                                                                                                                          |      |    |
| Settlements                                                                                                                                                                                                    | (11)           | (7) |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       | (16)           | (33) |
| Balance, Ending, Assets                                                                                                                                                                                        | 450            | 447 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Commercial mortgage-backed [Member]                                                                                                                                                                            |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 129            | 59 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | 1              |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 5              | 4 |
| Purchases                                                                                                                                                                                                      | 73             | 42 |
| Sales                                                                                                                                                                                                          |      |    |
| Settlements                                                                                                                                                                                                    | (7)            |    |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       | (24)           |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 177            | 105 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Other asset-backed [Member]                                                                                                                                                                                    |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 368            | 343 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | 3              | 4 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 1              | 4 |
| Purchases                                                                                                                                                                                                      | 136            | 176 |
| Sales                                                                                                                                                                                                          | (99)           | (77) |
| Settlements                                                                                                                                                                                                    | (13)           | (25) |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      | (41) |
| Balance, Ending, Assets                                                                                                                                                                                        | 396            | 384 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Total asset-backed [Member]                                                                                                                                                                                    |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 910            | 854 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | 7              | 5 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 6              | 4 |
| Purchases                                                                                                                                                                                                      | 270            | 256 |
| Sales                                                                                                                                                                                                          | (99)           | (77) |
| Settlements                                                                                                                                                                                                    | (31)           | (32) |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       | (40)           | (74) |
| Balance, Ending, Assets                                                                                                                                                                                        | 1,023          | 936 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Redeemable preferred stock [Member]                                                                                                                                                                            |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 26             |    |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  |      |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      |    |
| Purchases                                                                                                                                                                                                      |      | 53 |
| Sales                                                                                                                                                                                                          |      |    |
| Settlements                                                                                                                                                                                                    |      |    |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 26             | 53 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Fixed maturity securities [Member]                                                                                                                                                                             |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 1,251          | 1,507 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | 4              | 8 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 8              | 10 |
| Purchases                                                                                                                                                                                                      | 465            | 388 |
| Sales                                                                                                                                                                                                          | (163)          | (163) |
| Settlements                                                                                                                                                                                                    | (53)           | (51) |
| Transfers into Level 3                                                                                                                                                                                         | 26             | 33 |
| Transfers out of Level 3                                                                                                                                                                                       | (58)           | (84) |
| Balance, Ending, Assets                                                                                                                                                                                        | 1,480          | 1,648 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         | (1)            |    |
| Equity securities [Member]                                                                                                                                                                                     |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 34             | 67 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | (15)           |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             | 1              | (3) |
| Purchases                                                                                                                                                                                                      |      | 11 |
| Sales                                                                                                                                                                                                          |      | (1) |
| Settlements                                                                                                                                                                                                    |      |    |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       | (1)            |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 19             | 74 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         | (15)           | (2) |
| Other invested assets, including derivatives, net                                                                                                                                                              |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     |      | 10 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  |      |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      |    |
| Purchases                                                                                                                                                                                                      |      |    |
| Sales                                                                                                                                                                                                          | (1)            |    |
| Settlements                                                                                                                                                                                                    |      |    |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      |    |
| Balance, Ending, Assets                                                                                                                                                                                        | (1)            | 10 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Short term investments [Member]                                                                                                                                                                                |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 6              | 27 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  |      |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      |    |
| Purchases                                                                                                                                                                                                      |      | 12 |
| Sales                                                                                                                                                                                                          | (1)            |    |
| Settlements                                                                                                                                                                                                    |      | (39) |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 5              |    |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |
| Life settlement contracts [Member]                                                                                                                                                                             |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 100            | 117 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  | 7              | 3 |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      |    |
| Purchases                                                                                                                                                                                                      |      |    |
| Sales                                                                                                                                                                                                          |      |    |
| Settlements                                                                                                                                                                                                    | (12)           | (5) |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 95             | 115 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      | (1) |
| Separate account business [Member]                                                                                                                                                                             |           |   |
| **Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]**                                                                                              |           |   |
| Balance, Beginning, Assets                                                                                                                                                                                     | 2              | 23 |
| Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)                                                                                  |      |    |
| Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)                                                                                                             |      |    |
| Purchases                                                                                                                                                                                                      |      |    |
| Sales                                                                                                                                                                                                          |      | (19) |
| Settlements                                                                                                                                                                                                    |      |    |
| Transfers into Level 3                                                                                                                                                                                         |      |    |
| Transfers out of Level 3                                                                                                                                                                                       |      |    |
| Balance, Ending, Assets                                                                                                                                                                                        | 2              | 4 |
| Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)                                                                                         |      |    |

| X                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Unrealized gains (losses) Recognized in Net Income on Level 3 Assets and Liabilities Held
+ References
No definition available.
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| X                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).
+ 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 (c)(1) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of gain (loss) recognized in other comprehensive income, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).
+ 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 (c)(1a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.
+ 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.
+ 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Settlements that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.
+ 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Transfers into assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.
+ 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 (c)(3) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Transfers out of assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.
+ 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 (c)(3) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.
+ 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 (c) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c -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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