ASC 606 Adoption And Revenue Recognition (Disaggregation Of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,065	$ 2,106	$ 4,167	$ 4,265
Subsidy and other regulatory revenue	97	198	194	395
Total revenue	2,162	2,304	4,361	4,660
Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	973	974	1,958	1,967
Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	682	724	1,384	1,475
Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	270	329	550	676
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	140	79	275	147
Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,095	1,124	2,223	2,288
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	970	$ 982	1,944	$ 1,977
Amounts Excluding Adoption Of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,979		3,985
Subsidy and other regulatory revenue	181		368
Total revenue	2,160		4,353
Amounts Excluding Adoption Of ASC 606 [Member] | Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	948		1,890
Amounts Excluding Adoption Of ASC 606 [Member] | Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	648		1,318
Amounts Excluding Adoption Of ASC 606 [Member] | Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	297		606
Amounts Excluding Adoption Of ASC 606 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	86		171
Amounts Excluding Adoption Of ASC 606 [Member] | Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,068		2,157
Amounts Excluding Adoption Of ASC 606 [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	911		1,828
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(86)		(182)
Subsidy and other regulatory revenue	84		174
Total revenue	(2)		(8)
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member] | Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(25)		(68)
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member] | Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(34)		(66)
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member] | Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	27		56
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(54)		(104)
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member] | Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(27)		(66)
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ (59)		$ (116)