Description Of Business And Summary Of Significant Accounting Policies (Narrative) (Details) customer in Millions, $ in Millions		12 Months Ended
	Jul. 10, 2017 shares	Dec. 31, 2017 USD ($) employee state segment customer shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Jan. 31, 2018 USD ($)
Number of customers | customer		4.9
Number of subscribers | customer		3.9
Number of employees | employee		22,700
Number of states of operation | state		29
Reverse stock split, conversion ratio	0.0667
Common stock, shares issued (in shares)	80,000,000	79,532,000	79,532,000
Common stock, shares outstanding (in shares)	79,000,000	78,441,000	78,170,000
Common Stock, Shares Authorized	175,000,000	175,000,000	175,000,000
Reverse Stock Split, Fractional Shares Issued	0
Restricted Cash | $		$ 14
Customer surcharges | $		$ 216	$ 217	$ 151
Number of operating regions | segment		1
Subsequent Event [Member]
Restricted Cash | $					$ 7
Scenario, Previously Reported [Member]
Common stock, shares issued (in shares)			1,193,000,000
Common stock, shares outstanding (in shares)			1,178,000,000
Common Stock, Shares Authorized			1,750,000,000