Property, Plant, And Equipment (Property, Plant And Equipment, Net) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 27,695	$ 26,552
Less: Accumulated depreciation	(14,764)	(13,589)
Property, plant and equipment, net	12,931	12,963
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	212	217
Buildings and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,139	2,171
Estimated useful lives	40 years
General Support [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,643	1,624
General Support [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	15 years
General Support [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Central Office Electronic Circuit Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 8,270	7,968
Central Office Electronic Circuit Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	8 years
Central Office Electronic Circuit Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Poles [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,371	1,274
Estimated useful lives	30 years
Cable, Fiber and Wire [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 11,883	11,312
Cable, Fiber and Wire [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years
Cable, Fiber and Wire [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	15 years
Conduit [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,619	1,608
Estimated useful lives	50 years
Construction Work In Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 558	$ 378