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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 751		$ 751		$ 787	$ 819
Contract acquisition costs	97		97		87
Prepaid expenses	90		90			78
Other current assets	106		106		68	64
Property, plant and equipment, net	14,282		14,282		14,392	14,377
Other assets	236		236		224	97
Other current liabilities	387		387		335	330
Other liabilities	274		274		308	317
Deferred income taxes	1,219		1,219		1,190	1,139
Accumulated deficit	(2,107)		(2,107)		(2,109)	$ (2,263)
Revenue	2,162	$ 2,304	4,361	$ 4,660
Network access expenses	369	408	741	819
Network related expenses	478	477	961	970
Selling, general and administrative expenses	460	531	929	1,073
Other operating expenses	488		997
Total operating expenses	1,795	2,679	3,628	4,718
Operating income (loss)	367	$ (375)	733	$ (58)
Amounts Excluding Adoption Of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	786		786
Prepaid expenses	96		96
Other current assets	104		104
Property, plant and equipment, net	14,243		14,243
Other assets	99		99
Other current liabilities	375		375
Other liabilities	279		279
Deferred income taxes	1,165		1,165
Accumulated deficit	(2,280)		(2,280)
Revenue	2,160		4,353
Network access expenses	366		735
Network related expenses	478		961
Selling, general and administrative expenses	469		942
Other operating expenses	488		997
Total operating expenses	1,801		3,635
Operating income (loss)	359		718
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	35		35		(32)
Contract acquisition costs	(97)		(97)		87
Prepaid expenses	6		6
Other current assets	(2)		(2)		4
Property, plant and equipment, net	(39)		(39)		15
Other assets	(137)		(137)		127
Other current liabilities	(12)		(12)		5
Other liabilities	5		5		(9)
Deferred income taxes	(54)		(54)		51
Accumulated deficit	(173)		(173)		$ 154
Revenue	(2)		(8)
Network access expenses	(3)		(6)
Selling, general and administrative expenses	9		13
Total operating expenses	6		7
Operating income (loss)	$ (8)		$ (15)