Commitments And Contingencies (Narrative) (Details) $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2018 property county item	Aug. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) state property	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Regulatory Commitments [Abstract]
Number of states of operation | state			29
Number of auctions | item	2
Operating Leases [Abstract]
Term Of Lease Arrangements Lower Range			1 year
Term Of Lease Arrangements Upper Range			99 years
Rental expense			$ 102	$ 106	$ 137
FCC Inquiry [Member]
Regulatory Commitments [Abstract]
Award in funding		$ 200
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
Auction 101 [Member]
Regulatory Commitments [Abstract]
Number of licenses | item	2
Number of counties | county	1,536
Auction 102 [Member]
Regulatory Commitments [Abstract]
Number of licenses | item	7
Number of economic areas | property	416
CTF Acquisition [Member] | CAF Phase II [Member]
Regulatory Commitments [Abstract]
Annual support offered by the Federal Communications Commission			$ 49