Summary Of Significant Accounting Policies (Schedule Of Revenues From External Customers) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 2,356	$ 1,355
Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	2,159	1,189
Switched Access And Subsidy Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	197	166
Data And Internet Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	993	587
Voice Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	751	467
Video Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	347	67
Other [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	$ 68	$ 68