Description Of Business And Summary Of Significant Accounting Policies (Schedule Of Revenue From External Customers) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information
Revenues	$ 2,217	$ 2,251	$ 2,304	$ 2,356	$ 2,409	$ 2,524	$ 2,608	$ 1,355	$ 9,128	$ 8,896	$ 5,576
Customer Revenue [Member]
Segment Reporting Information
Revenues									8,352	8,099	4,899
Voice Services [Member]
Segment Reporting Information
Revenues									2,864	2,886	2,022
Data And Internet Services [Member]
Segment Reporting Information
Revenues									3,862	3,693	2,337
Video Services [Member]
Segment Reporting Information
Revenues									1,304	1,244	285
Other Customer Revenues [Member]
Segment Reporting Information
Revenues									322	276	255
Switched Access And Subsidy Revenue [Member]
Segment Reporting Information
Revenues									$ 776	$ 797	$ 677