| **Organization Review Costs by Reportable Segment (Details) - USD ($) $ in Millions** | 3 Months Ended | 9 Months Ended |
|---------------------------------------------------------------------------------------|----------------|----------------|
||
| **Restructuring Cost and Reserve [Line Items]**                                       |           |           |
| Restructuring Costs                                                                   | $ 11           | $ 17           |
| Specialty [Member]                                                                    |           |           |
| **Restructuring Cost and Reserve [Line Items]**                                       |           |           |
| Restructuring Costs                                                                   | 3              | 4              |
| Commercial [Member]                                                                   |           |           |
| **Restructuring Cost and Reserve [Line Items]**                                       |           |           |
| Restructuring Costs                                                                   | 7              | 12             |
| International [Member]                                                                |           |           |
| **Restructuring Cost and Reserve [Line Items]**                                       |           |           |
| Restructuring Costs                                                                   | 0              | 0              |
| Life and Group Non-Core [Member]                                                      |           |           |
| **Restructuring Cost and Reserve [Line Items]**                                       |           |           |
| Restructuring Costs                                                                   | 1              | 1              |
| Corporate and Other Non-Core [Member]                                                 |           |           |
| **Restructuring Cost and Reserve [Line Items]**                                       |           |           |
| Restructuring Costs                                                                   | $ 0            | $ 0            |

| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585
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| X                                                                                                                                                 |
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| X                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
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