Commitments And Contingencies (Narrative) (Details) - Jun. 30, 2015 $ in Millions	USD ($) item / S entity
Regulatory Commitments [Abstract]
Percentage of households to have broadband availability and speeds of 3 Mbps by year 2013 (in hundredths)	85.00%
Targeted minimum megabits per second in markets acquired by year 2013 (in Mbps) | item / S	3
Targeted minimum megabits per second in markets acquired by year 2015 (in Mbps) | item / S	4
Percentage of households to have broadband availability and speeds of 4 Mbps by year 2013	75.00%
Percentage of households to have broadband availability and speeds of 4 Mbps by year 2014	80.00%
Percentage of households to have broadband availability and speeds of 4 Mbps by year 2015	85.00%
Annual support offered by the Federal Communications Commission	$ 283
Number of households to be serviced under regulatory funded programs	660,000
Number of States in our Territory	28
Unconditional Purchase Obligation [Abstract]
Commitment under the arrangement in 2015	$ 141
Vermont Joint Owners Consortium [Abstract]
Number of utilities forming the Vermont Joint Owners consortium | entity	14
Purchase power obligation (in hundredths)	10.00%
Undiscounted purchase obligation if members of the consortium remained in default for the duration of the contract	$ 60
Minimum [Member]
Estimated Future Capital Expenditures For Business Operations	700
Maximum [Member]
Estimated Future Capital Expenditures For Business Operations	$ 750