Investments In Equity Securities (Details) - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Marketable Securities [Line Items] | ||
| Investments in equity securities | $ 611 | $ 2,363 |
| Charter | ||
| Marketable Securities [Line Items] | ||
| Investments in equity securities | 1,800 | |
| ILG | ||
| Marketable Securities [Line Items] | ||
| Investments in equity securities | 518 | 474 |
| Other Investments | ||
| Marketable Securities [Line Items] | ||
| Investments in equity securities | $ 93 | $ 89 |