ASC 606 Adoption And Revenue Recognition (Disaggregation Of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,031	$ 2,060	$ 6,198	$ 6,325
Subsidy and other regulatory revenue	95	191	289	586
Total revenue	2,126	2,251	6,487	6,911
Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	961	956	2,919	2,923
Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	669	702	2,053	2,177
Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	260	318	810	994
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	141	84	416	231
Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,069	1,102	3,292	3,390
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	962	$ 958	2,906	$ 2,935
Amounts Excluding Adoption Of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,947		5,932
Subsidy and other regulatory revenue	173		541
Total revenue	2,120		6,473
Amounts Excluding Adoption Of ASC 606 [Member] | Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	938		2,828
Amounts Excluding Adoption Of ASC 606 [Member] | Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	634		1,952
Amounts Excluding Adoption Of ASC 606 [Member] | Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	287		893
Amounts Excluding Adoption Of ASC 606 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	88		259
Amounts Excluding Adoption Of ASC 606 [Member] | Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,047		3,204
Amounts Excluding Adoption Of ASC 606 [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	900		2,728
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(84)		(266)
Subsidy and other regulatory revenue	78		252
Total revenue	(6)		(14)
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	(23)		(91)
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	(35)		(101)
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		83
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	(53)		(157)
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	(22)		(88)
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	$ (62)		$ (178)