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