Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Abstract]
Number of reportable segments | segment			1
Customer surcharges	$ 60	$ 50	$ 162	$ 160
Video franchise fees	10	$ 11	$ 31	$ 35
Number of operating segments | segment			1
Restricted cash	$ 50		$ 50		$ 50
Expected customer life	4 years		4 years
Funding term			6 years