Commitments And Contingencies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) state
Operating Leases [Abstract]
Term of lease arrangements lower range	1 year
rm of lease arrangements lower range	99 years
CAF Phase II [ Member]
Regulatory Commitments [Abstract]
Annual support offered by the Federal Communications Commission	$ 332
Number of households to be serviced under regulatory funded programs	774,000
Amount of annual USF frozen high-cost support	$ 198
Number of states of operation | state	29
CAF II Four States [Member]
Regulatory Commitments [Abstract]
Annual support offered by the Federal Communications Commission	$ 19
Number of states of operation | state	4