| **Fair Value Measurements (Details) (Recurring basis, USD $)In Millions, unless otherwise specified** | Sep. 30, 2013 | Dec. 31, 2012 |
|-------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Assets**                                                                                            |          |          |
| Derivative financial instruments, net                                                                 | $ 150         | $ 223         |
| Total Assets                                                                                          | 150           | 223           |
| **Liabilities**                                                                                       |          |          |
| Guarantees                                                                                            | 3             | 2             |
| Total Liabilities                                                                                     | 3             | 2             |
| Level 1                                                                                               |          |          |
| **Assets**                                                                                            |          |          |
| Derivative financial instruments, net                                                                 | 0             | 0             |
| Total Assets                                                                                          | 0             | 0             |
| **Liabilities**                                                                                       |          |          |
| Guarantees                                                                                            | 0             | 0             |
| Total Liabilities                                                                                     | 0             | 0             |
| Level 2                                                                                               |          |          |
| **Assets**                                                                                            |          |          |
| Derivative financial instruments, net                                                                 | 150           | 223           |
| Total Assets                                                                                          | 150           | 223           |
| **Liabilities**                                                                                       |          |          |
| Guarantees                                                                                            | 0             | 0             |
| Total Liabilities                                                                                     | 0             | 0             |
| Level 3                                                                                               |          |          |
| **Assets**                                                                                            |          |          |
| Derivative financial instruments, net                                                                 | 0             | 0             |
| Total Assets                                                                                          | 0             | 0             |
| **Liabilities**                                                                                       |          |          |
| Guarantees                                                                                            | 3             | 2             |
| Total Liabilities                                                                                     | $ 3           | $ 2           |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258
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| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of guarantee, including, but not limited to, financial standby letter of credit, fair value guarantee, guarantee of collection of scheduled contractual cash flows from financial assets, and contracts that contingently require the guarantor to make payments or perform services.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12201-110248
+ Details**Name:**us-gaap_GuaranteesFairValueDisclosure**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of financial and nonfinancial obligations.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258
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| X                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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