Description Of Business And Summary Of Significant Accounting Policies (Schedule Of Revenues From External Customers) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 1,413	$ 1,424	$ 1,368	$ 1,371	$ 1,330	$ 1,141	$ 1,147	$ 1,154	$ 5,576	$ 4,772	$ 4,762
Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									4,899	4,253	4,210
Switched Access And Subsidy Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									677	519	552
Voice Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									2,022	1,951	2,045
Data And Internet Services [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									2,337	1,948	1,866
Other Customer Revenues [Member] | Customer Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									$ 540	$ 354	$ 299