Recent Accounting Literature (Schedule Of Impact Of Adoption Of ASU 2017-07) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Network related expenses	$ 483	$ 493
Selling, general and administrative expenses	469	542
Investment and other income, net	$ 8
Pension settlement costs		43
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Network related expenses		494
Selling, general and administrative expenses		544
Pension settlement costs		43
Investment and other income, net		3
Accounting Standards Update 2017-07 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Network related expenses		(1)
Selling, general and administrative expenses		(2)
Pension settlement costs		(43)
Investment and other income, net		(3)
Pension settlement costs		$ 43