| **Benefit Plans (Reconciliation of Level 3 Plan Assets) (Details) - USD ($) $ in Millions** | 12 Months Ended |
|---------------------------------------------------------------------------------------------|-----------------|
||
| Corporate and other bonds [Member]                                                          |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | $ 478           |   |
| Fair value of plan assets at December 31                                                    | 465             | $ 478 |
| Fixed Maturities [Member]                                                                   |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 793             |   |
| Fair value of plan assets at December 31                                                    | 784             | 793 |
| Equity securities [Member]                                                                  |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 507             |   |
| Fair value of plan assets at December 31                                                    | 443             | 507 |
| Hedge Funds [Member]                                                                        |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 865             |   |
| Fair value of plan assets at December 31                                                    | 812             | 865 |
| Private Equity Funds [Member]                                                               |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 113             |   |
| Fair value of plan assets at December 31                                                    | 123             | 113 |
| Total limited partnerships [Member]                                                         |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 978             |   |
| Fair value of plan assets at December 31                                                    | 935             | 978 |
| Total assets [Member]                                                                       |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 2,456           |   |
| Fair value of plan assets at December 31                                                    | 2,267           | 2,456 |
| Fair Value, Inputs, Level 3 [Member] | Corporate and other bonds [Member]                   |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 15              | 15 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               | 0               | 0 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       | 0               | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     | 0               | 0 |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   | (5)             | 0 |
| Fair value of plan assets at December 31                                                    | 10              | 15 |
| Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member]                            |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 15              | 15 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               | 0               | 0 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       | 0               | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     | 0               | 0 |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   | (5)             | 0 |
| Fair value of plan assets at December 31                                                    | 10              | 15 |
| Fair Value, Inputs, Level 3 [Member] | Equity securities [Member]                           |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 0               | 8 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               |            | 0 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       |            | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     |            | (8) |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   |            | 0 |
| Fair value of plan assets at December 31                                                    | 0               | 0 |
| Fair Value, Inputs, Level 3 [Member] | Hedge Funds [Member]                                 |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 303             | 322 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               | 18              | 19 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       | 0               | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     | (25)            | (38) |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   | 0               | 0 |
| Fair value of plan assets at December 31                                                    | 296             | 303 |
| Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]                        |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 113             | 114 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               | 9               | 19 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       | 0               | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     | 1               | (20) |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   | 0               | 0 |
| Fair value of plan assets at December 31                                                    | 123             | 113 |
| Fair Value, Inputs, Level 3 [Member] | Total limited partnerships [Member]                  |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 416             | 436 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               | 27              | 38 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       | 0               | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     | (24)            | (58) |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   | 0               | 0 |
| Fair value of plan assets at December 31                                                    | 419             | 416 |
| Fair Value, Inputs, Level 3 [Member] | Total assets [Member]                                |            |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                            |            |   |
| Fair value of plan assets at January 1                                                      | 431             | 459 |
| Defined Benefit Plan, Actual Return on Plan Assets Still Held                               | 27              | 38 |
| Defined Benefit Plan, Actual Return on Plan Assets Sold During Period                       | 0               | 0 |
| Defined Benefit Plan, Purchases, Sales, and Settlements                                     | (24)            | (66) |
| Defined Benefit Plan, Net transfers into (out of) Level 3                                   | (5)             | 0 |
| Fair value of plan assets at December 31                                                    | $ 429           | $ 431 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Actual return on plan assets, separately identifying the amount related to assets sold during the period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02)(A) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c)(iv)(02)(A) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02)(A) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c)(iv)(02)(A) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920
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| 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
Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 50 -URI http://asc.fasb.org/extlink&oid=49178875&loc=d3e12355-114930Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase (decrease) in plan assets from purchases, sales and settlement of plan obligations.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02)(B) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c)(iv)(02)(B) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Transfers in and out of Level 3. For example, transfers due to changes in the observability of significant inputs.
+ References
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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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| X                                                                                                                                                                             |
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| X                                                                                                                                                                                                |
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| X                                                                                                                                                                          |
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