Derivative Instruments And Hedging Activities (Number Of Derivative Contracts By Commodity Type) (Details)	12 Months Ended
	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Number of Capacity Contracts	1,328	[1]
Description Of Derivative Activity Volume Electric Derivatives [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts	687	[1]
MWhs	15,602,445	[2]
Number of Capacity Contracts	46	[1]
MWs	6,499	[2]
Description Of Derivative Activity Volume Gas Derivatives [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts	595	[1]
Dths	97,101,500	[2]

[1] Qualifying derivative contracts, which have been designated as normal purchases or normal sales contracts, are not reported at fair value under the accounting rules for derivatives and hedging and, therefore, are excluded from the table.

[2] Volumes are reported net of long and short positions.