| **Short-Term Borrowings (Details) (USD $)In Millions, unless otherwise specified** | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 |
|------------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Short-term Debt**                                                                |          |          |          |
| Short-term borrowings, Balance                                                     | $ 4,651       | $ 3,895       | $ 3,852       |
| Commercial paper, net                                                              |          |          |          |
| **Short-term Debt**                                                                |          |          |          |
| Short-term borrowings, Balance                                                     | 3,654         | 2,818         | 2,710         |
| Short-term borrowings, Avg. Rate                                                   | 0.60%         | 1.00%         | 1.50%         |
| Bank borrowings                                                                    |          |          |          |
| **Short-term Debt**                                                                |          |          |          |
| Short-term borrowings, Balance                                                     | 418           | 527           | 479           |
| Short-term borrowings, Avg. Rate                                                   | 5.60%         | 7.30%         | 4.90%         |
| Variable denomination floating rate demand notes                                   |          |          |          |
| **Short-term Debt**                                                                |          |          |          |
| Short-term borrowings, Balance                                                     | $ 579         | $ 550         | $ 663         |
| Short-term borrowings, Avg. Rate                                                   | 0.80%         | 0.90%         | 1.10%         |

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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.
+ References
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| X                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ShortTermDebtLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of short-term debt outstanding by type or by instrument at that time.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph b -Article 5
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