Revenue Recognition (Disaggregation Of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									$ 7,738	$ 8,228	$ 8,352
Subsidy and other regulatory revenue									369	383	776
Total revenue	$ 1,942	$ 1,997	$ 2,067	$ 2,101	$ 2,124	$ 2,126	$ 2,162	$ 2,199	8,107	8,611	9,128
Data And Internet Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									3,756	3,878	3,862
Voice Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									2,500	2,721	2,864
Video Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									1,005	1,085	1,304
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									477	544	322
Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									4,153	4,380	4,476
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers									$ 3,585	$ 3,848	$ 3,876