Assets And Liabilities Measured At Fair Value (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions |
Mar. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash equivalents | $ 667 | $ 625 |
| Available-for-sale securities | 2,104 | 1,846 |
| Investments in and Advances to Affiliates, at Fair Value | 3,688 | 3,161 |
| Debt | 1,746 | 1,667 |
| Fair Value, Inputs (Level 1) | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash equivalents | 667 | 625 |
| Available-for-sale securities | 2,104 | 1,846 |
| Investments in and Advances to Affiliates, at Fair Value | 3,688 | 3,161 |
| Significant Other Observable Inputs (Level 2) | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Debt | $ 1,746 | $ 1,667 |