ASC 606 Adoption And Revenue Recognition (Schedule Of Impact Of New Accounting Pronouncement On Balance Sheet And Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 744		$ 744		$ 787	$ 819
Contract acquisition costs	102		102		87
Prepaid expenses	95		95			78
Other current assets	103		103		68	64
Property, plant and equipment, net	14,268		14,268		14,392	14,377
Other assets	233		233		224	97
Other current liabilities	324		324		335	330
Other liabilities	296		296		308	317
Deferred income taxes	1,204		1,204		1,190	1,139
Accumulated deficit	(2,533)		(2,533)		(2,109)	$ (2,263)
Revenue	2,126	$ 2,251	6,487	$ 6,911
Network access expenses	353	390	1,094	1,209
Network related expenses	476	498	1,437	1,468
Selling, general and administrative expenses	445	487	1,374	1,560
Other operating expenses	885		1,882
Total operating expenses	2,159	1,929	5,787	6,647
Operating income (loss)	(33)	$ 322	700	$ 264
Amounts Excluding Adoption Of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	782		782
Prepaid expenses	100		100
Other current assets	107		107
Property, plant and equipment, net	14,221		14,221
Other assets	101		101
Other current liabilities	320		320
Other liabilities	299		299
Deferred income taxes	1,152		1,152
Accumulated deficit	(2,714)		(2,714)
Revenue	2,120		6,473
Network access expenses	354		1,089
Network related expenses	476		1,437
Selling, general and administrative expenses	447		1,389
Other operating expenses	885		1,882
Total operating expenses	2,162		5,797
Operating income (loss)	(42)		676
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	38		38		(32)
Contract acquisition costs	(102)		(102)		87
Prepaid expenses	5		5
Other current assets	4		4		4
Property, plant and equipment, net	(47)		(47)		15
Other assets	(132)		(132)		127
Other current liabilities	(4)		(4)		5
Other liabilities	3		3		(9)
Deferred income taxes	(52)		(52)		51
Accumulated deficit	(181)		(181)		$ 154
Revenue	(6)		(14)
Network access expenses	1		(5)
Selling, general and administrative expenses	2		15
Total operating expenses	3		10
Operating income (loss)	$ (9)		$ (24)