Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 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)	3
Targeted minimum megabits per second in markets acquired by year 2015 (in Mbps)	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%
Percentage of households throughout acquired Territories with broadband availability in excess of 4 Mbps (in hundredths)	84.80%
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	14
Purchase power obligation (in hundredths)	10.00%
Number of years assumed if members of the consortium remained in default for the duration of the contract	8 months
Undiscounted purchase obligation if members of the consortium remained in default for the duration of the contract	96
Minimum [Member]
Estimated Future Capital Expenditures For Business Operations	650
Maximum [Member]
Estimated Future Capital Expenditures For Business Operations	$ 700