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
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 778		$ 787	$ 819
Prepaid expenses	78			78
Contract acquisition costs	91		87
Other current assets	54		68	64
Property, plant and equipment, net	14,321		14,392	14,377
Other assets	228		224	97
Other current liabilities	334		335	330
Other liabilities	280		308	317
Deferred income taxes	1,217		1,190	1,139
Accumulated deficit	(2,089)		(2,109)	$ (2,263)
Revenue	2,199	$ 2,356
Network access expenses	372	411
Network related expenses	483	493
Selling, general and administrative expenses	469	542
Other operating expenses	509
Total operating expenses	1,833	2,039
Operating income	366	$ 317
Amounts Without Adoption Of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	810
Prepaid expenses	82
Other current assets	52
Property, plant and equipment, net	14,297
Other assets	98
Other current liabilities	325
Other liabilities	290
Deferred income taxes	1,164
Accumulated deficit	(2,248)
Revenue	2,193
Network access expenses	369
Network related expenses	483
Selling, general and administrative expenses	473
Other operating expenses	509
Total operating expenses	1,834
Operating income	359
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	32		(32)
Prepaid expenses	4
Contract acquisition costs	(91)		87
Other current assets	(2)		4
Property, plant and equipment, net	(24)		15
Other assets	(130)		127
Other current liabilities	(9)		5
Other liabilities	10		(9)
Deferred income taxes	(53)		51
Accumulated deficit	(159)		$ 154
Revenue	(6)
Network access expenses	(3)
Selling, general and administrative expenses	4
Total operating expenses	1
Operating income	$ (7)