Assets And Liabilities Measured At Fair Value (Details) - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | Ìý | Ìý |
| Cash equivalents | $ 824 | $ 804 |
| Debt and equity securities | 1,502 | 1,047 |
| Financial instrument assets | 416 | 369 |
| Debt | 2,482 | 2,115 |
| Level 1 | Ìý | Ìý |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | Ìý | Ìý |
| Cash equivalents | 824 | 804 |
| Debt and equity securities | 471 | 467 |
| Financial instrument assets | 21 | 19 |
| Level 2 | Ìý | Ìý |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | Ìý | Ìý |
| Debt and equity securities | 1,031 | 580 |
| Financial instrument assets | 395 | 350 |
| Debt | $ 2,482 | $ 2,115 |
| X |
- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristic |