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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 723				$ 819				$ 723	$ 819		$ 787
Contract acquisition costs	107								107			87
Prepaid expenses	86				78				86	78
Other current assets	60				64				60	64		68
Property, plant and equipment, net	14,187				14,377				14,187	14,377		14,392
Other assets	265				97				265	97		224
Other current liabilities	303				330				303	330		335
Other liabilities	281				317				281	317		308
Deferred income taxes	1,109				1,139				1,109	1,139		1,190
Accumulated deficit	(2,752)				(2,263)				(2,752)	(2,263)		$ (2,109)
Revenue	2,124	$ 2,126	$ 2,162	$ 2,199	2,217	$ 2,251	$ 2,304	$ 2,356	8,611	9,128	$ 8,896
Network access expenses									1,441	1,597	1,470
Network related expenses									1,898	1,958	1,876
Selling, general and administrative expenses									1,815	2,017	2,081
Other operating expenses									2,630
Total operating expenses									7,784
Operating income (loss)	127	$ (33)	$ 367	$ 366	(1,747)	$ 322	$ (375)	$ 317	827	(1,483)	$ 911
Impact Of Adoption Of ACS 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	44				(32)				44	(32)
Contract acquisition costs	(107)				87				(107)	87
Prepaid expenses	3								3
Other current assets	(4)				4				(4)	4
Property, plant and equipment, net	(56)				15				(56)	15
Other assets	(117)				127				(117)	127
Other current liabilities	(6)				5				(6)	5
Other liabilities	10				(9)				10	(9)
Deferred income taxes	(57)				51				(57)	51
Accumulated deficit	(184)				$ 154				(184)	$ 154
Revenue									(15)
Total operating expenses									15
Operating income (loss)									(30)
Impact Of Adoption Of ACS 606 [Member] | Accounting Standards Update 2014-09 [Member] | Restatement Adjustment [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue									(15)
Network access expenses									(3)
Selling, general and administrative expenses									19
Other operating expenses									(1)
Total operating expenses									15
Operating income (loss)									(30)
Amounts Excluding Adoption of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	767								767
Prepaid expenses	89								89
Other current assets	56								56
Property, plant and equipment, net	14,131								14,131
Other assets	148								148
Other current liabilities	297								297
Other liabilities	291								291
Deferred income taxes	1,052								1,052
Accumulated deficit	$ (2,936)								(2,936)
Revenue									8,596
Network access expenses									1,438
Network related expenses									1,898
Selling, general and administrative expenses									1,834
Other operating expenses									2,629
Total operating expenses									7,799
Operating income (loss)									$ 797