ASC 606 Adoption And Revenue Recognition (Disaggregation Of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,102	$ 2,159
Revenue	2,199	2,356
Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	985	993
Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	702	751
Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	280	347
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	135	68
Subsidy And Other Regulatory Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue	97	197
Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,128	1,164
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	974	$ 995
Amounts Without Adoption Of ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,006
Revenue	2,193
Amounts Without Adoption Of ASC 606 [Member] | Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	942
Amounts Without Adoption Of ASC 606 [Member] | Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	670
Amounts Without Adoption Of ASC 606 [Member] | Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	309
Amounts Without Adoption Of ASC 606 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85
Amounts Without Adoption Of ASC 606 [Member] | Subsidy And Other Regulatory Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue	187
Amounts Without Adoption Of ASC 606 [Member] | Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,089
Amounts Without Adoption Of ASC 606 [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	917
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(96)
Revenue	(6)
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(43)
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(32)
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	29
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(50)
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Subsidy And Other Regulatory Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue	90
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(39)
Accounting Standards Update 2014-09 [Member] | Adjustments For ASC 606 [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ (57)