| **Derivative Financial Instruments (Summary of aggregate contractual or notional amounts and gross estimated fair values related to derivative financial instruments) (Details) (USD $)In Millions, unless otherwise specified** | Sep. 30, 2013 | Dec. 31, 2012 |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Derivative [Line Items]**                                                                                                                                                                                                      |          |          |
| Contractual/notional amount                                                                                                                                                                                                      | $ 69          | $ 84          |
| Estimated fair value asset                                                                                                                                                                                                       |     |     |
| Estimated fair value (liability)                                                                                                                                                                                                 | (1)           | (3)           |
| Derivative Instruments Without Hedge Designation [Member]                                                                                                                                                                        |          |          |
| **Derivative [Line Items]**                                                                                                                                                                                                      |          |          |
| Contractual/notional amount                                                                                                                                                                                                      | 52            | 84            |
| Estimated fair value asset                                                                                                                                                                                                       |     |     |
| Estimated fair value (liability)                                                                                                                                                                                                 | (1)           | (3)           |
| Derivative Instruments Without Hedge Designation [Member] | Credit default swap - purchased protection [Member]                                                                                                                  |          |          |
| **Derivative [Line Items]**                                                                                                                                                                                                      |          |          |
| Contractual/notional amount                                                                                                                                                                                                      | 20            | 20            |
| Estimated fair value asset                                                                                                                                                                                                       |     |     |
| Estimated fair value (liability)                                                                                                                                                                                                 |     | (1)           |
| Derivative Instruments Without Hedge Designation [Member] | Currency forwards [Member]                                                                                                                                           |          |          |
| **Derivative [Line Items]**                                                                                                                                                                                                      |          |          |
| Contractual/notional amount                                                                                                                                                                                                      | 27            | 59            |
| Estimated fair value asset                                                                                                                                                                                                       |     |     |
| Estimated fair value (liability)                                                                                                                                                                                                 | (1)           | (2)           |
| Derivative Instruments Without Hedge Designation [Member] | Equity warrants [Member]                                                                                                                                             |          |          |
| **Derivative [Line Items]**                                                                                                                                                                                                      |          |          |
| Contractual/notional amount                                                                                                                                                                                                      | 5             | 5             |
| Estimated fair value asset                                                                                                                                                                                                       |     |     |
| Estimated fair value (liability)                                                                                                                                                                                                 |     |     |
| Trading activities [Member] | Futures Sold, Not yet Purchased [Member]                                                                                                                                                           |          |          |
| **Derivative [Line Items]**                                                                                                                                                                                                      |          |          |
| Contractual/notional amount                                                                                                                                                                                                      | 17            |          |
| Estimated fair value asset                                                                                                                                                                                                       |     |          |
| Estimated fair value (liability)                                                                                                                                                                                                 |     |          |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of derivative asset, 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
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                                                                                                                                                       |
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