Recent Accounting Pronouncements (Schedule Of Impact Of Adoption Of ASU 2017-07) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Network related expenses	$ 1,898	$ 1,958	$ 1,876
Selling, general and administrative expenses	1,815	2,017	2,081
Investment and other income, net	13	1	4
Pension settlement costs	$ 41	83
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Network related expenses		1,959	1,887
Selling, general and administrative expenses		2,018	2,093
Pension settlement costs		83
Investment and other income, net		3	27
Restatement Adjustment [Member] | Accounting Standards Update 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Network related expenses		(1)	(11)
Selling, general and administrative expenses		(1)	(12)
Pension settlement costs		(83)
Investment and other income, net		(2)	$ (23)
Pension settlement costs		$ 83