Assets And Liabilities Measured At Fair Value (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash equivalents | $ 295 | $ 2,225 |
| Short term marketable securities | 910 | |
| Available-for-sale securities | 1,742 | 1,294 |
| Investments in and Advances to Affiliates, at Fair Value | 3,051 | |
| Debt | 2,023 | 2,480 |
| Fair Value, Inputs (Level 1) | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash equivalents | 295 | 2,225 |
| Short term marketable securities | 331 | |
| Available-for-sale securities | 1,735 | 1,287 |
| Investments in and Advances to Affiliates, at Fair Value | 3,051 | |
| Significant Other Observable Inputs (Level 2) | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Short term marketable securities | 579 | |
| Available-for-sale securities | 7 | 7 |
| Debt | $ 2,023 | $ 2,480 |