Summary Of Significant Accounting Policies (Schedule Of Revenues From External Customers) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 2,304	$ 2,608	$ 4,660	$ 3,963
Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	2,106	2,381	4,265	3,570
Switched Access And Subsidy Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	198	227	395	393
Data And Internet Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	974	1,048	1,967	1,635
Voice Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	724	836	1,475	1,303
Video Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	329	419	676	487
Other [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	$ 79	$ 78	$ 147	$ 145