Revenue Recognition (Disaggregation Of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,705	$ 1,972	$ 3,548	$ 3,981
Subsidy and other revenue	96	95	186	187
Total revenue	1,801	2,067	3,734	4,168
Lease revenue	17	17	34	35
Divestiture revenue	10		10
Revenue from contracts with customers, performance obligation	3,048		3,048
Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	874	963	1,806	1,930
Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	523	629	1,095	1,279
Video services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	200	260	422	528
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	108	120	225	244
Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	899	1,050	1,870	2,127
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 806	$ 922	$ 1,678	$ 1,854