Assets And Liabilities Measured At Fair Value (Details) - USD ($) $ in Millions |
Mar. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | 听 | 听 |
| Cash equivalents | $ 631 | $ 289 |
| Available-for-sale securities | 518 | 489 |
| Financial instrument assets | 370 | 286 |
| Debt | 2,107 | 1,546 |
| Level 1 | 听 | 听 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | 听 | 听 |
| Cash equivalents | 631 | 289 |
| Available-for-sale securities | 518 | 489 |
| Financial instrument assets | 16 | 16 |
| Level 2 | 听 | 听 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | 听 | 听 |
| Financial instrument assets | 354 | 270 |
| Debt | $ 2,107 | $ 1,546 |
| X | ||||||||||
- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | |||||||||
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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