Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions		3 Months Ended
	Jul. 10, 2017 shares	Mar. 31, 2018 USD ($) segment shares	Mar. 31, 2017 USD ($)	Dec. 31, 2017 shares	Jul. 09, 2017 shares
Summary Of Significant Accounting Policies [Abstract]
Number of reportable segments | segment		1
Reverse stock split, conversion ratio	0.0667
Common Stock, Shares Authorized	175,000,000	175,000,000		175,000,000	1,750,000,000
Common stock, shares issued (in shares)	80,000,000	80,367,000		79,532,000	1,193,000,000
Common stock, shares outstanding (in shares)	79,000,000	80,251,000		78,441,000	1,178,000,000
Reverse Stock Split, Fractional Shares Issued	0
Customer surcharges | $		$ 57	$ 53
Video franchise fees | $		$ 12	$ 14
Number of operating segments | segment		1