| **Derivative Financial Instruments (Summary of recognized gains (losses) related to derivative financial instruments) (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended | 6 Months Ended |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Recognized Gains (Losses)**                                                                                                                                                    |           |           |   |   |
| Derivative instruments not designated as hedging instruments, gain (loss), net                                                                                                   | $ 1            |      |    | $ (1) |
| Derivative instruments, gain (loss) recognized in income, net                                                                                                                    | 1              |      | 1 | (1) |
| Currency forwards [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
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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
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