Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Abstract]
Number of reportable segments | segment			1
Customer surcharges	$ 50	$ 52	$ 160	$ 160
Video franchise fees	11	$ 13	35	$ 39
Restricted cash	$ 50		$ 50		$ 14