Commitments And Contingencies (Narrative) (Details) $ in Millions			3 Months Ended
	Dec. 07, 2020 USD ($) item shares	Jan. 30, 2020 USD ($)	Mar. 31, 2021 USD ($) state
CAF Phase II [Member]
Commitments And Contingencies [Line Items]
Number of states of operation | state			25
Annual support offered by the Federal Communications Commission			$ 313
RDOF Program, Phase I [Member]
Commitments And Contingencies [Line Items]
Award amount	$ 371
Period to build gigabit capable broadband	10 years
Number of location to build gigabit capable broadband | item	127,000
Number of states to build gigabit capable broadband | shares	8
Minimum [Member]
Commitments And Contingencies [Line Items]
Terms of lease arrangements			1 year
Minimum [Member] | RDOF Program, Phase II [Member]
Commitments And Contingencies [Line Items]
Annual support offered by the Federal Communications Commission		$ 11,200
Maximum [Member]
Commitments And Contingencies [Line Items]
Terms of lease arrangements			99 years