Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) state property	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Regulatory Commitments [Abstract]
Number of states of operation | state	29
Operating Leases [Abstract]
Term Of Lease Arrangements Lower Range	1 year
Term Of Lease Arrangements Upper Range	99 years
Rental expense	$ 106	$ 137	$ 119
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 | property	774,000
CTF Transaction [Member] | CAF Phase II [Member]
Regulatory Commitments [Abstract]
Annual support offered by the Federal Communications Commission	$ 49