| **Derivative Financial Instruments (Summary of recognized gains (losses) related to derivative financial instruments) (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended | 9 Months Ended |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
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| **Recognized Gains (Losses)**                                                                                                                                                    |           |           |   |   |
| Derivative instruments not designated as hedging instruments, gain (loss), net                                                                                                   | $ (1)          | $ 1            | $ (1) |    |
| Derivative instruments, gain (loss) recognized in income, net                                                                                                                    | (2)            | 1              | (1) |    |
| Currency forwards [Member]                                                                                                                                                       |           |           |   |   |
| **Recognized Gains (Losses)**                                                                                                                                                    |           |           |   |   |
| Derivative instruments not designated as hedging instruments, gain (loss), net                                                                                                   | (1)            |      | (1) | (1) |
| Forward commitments for mortgage-backed securities [Member]                                                                                                                      |           |           |   |   |
| **Recognized Gains (Losses)**                                                                                                                                                    |           |           |   |   |
| Derivative instruments not designated as hedging instruments, gain (loss), net                                                                                                   |      | 1              |    | 1 |
| Futures sold, not yet purchased [Member]                                                                                                                                         |           |           |   |   |
| **Recognized Gains (Losses)**                                                                                                                                                    |           |           |   |   |
| Gain (loss) on derivative instruments held for trading purposes, net                                                                                                             | $ (1)          |      |    |    |

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| - Definition
The amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.
+ References
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| - Definition
Net gain (loss) from the increase (decrease) in fair value of derivative instrument not designated as hedging instrument.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph b(1)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959
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| - Definition
Aggregate net gain and losses (whether realized or unrealized) on all derivative instruments held for trading purposes whether or not settled physically.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 02-3 -Paragraph 8 -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 Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41322-113958Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4F -URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624186-113959
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