Derivative Instruments And Hedging Activities (Number Of Derivative Contracts By Commodity Type) (Details)	6 Months Ended
	Jun. 30, 2011
Number of Energy Contracts	1,705	[1]
Description of Derivative Activity Volume Electric Derivatives [Member]
Number of Energy Contracts	882	[1]
MWhs	20,318,546	[2]
Number of Capacity Contracts	56	[1]
MWs	9,161	[2]
Description of Derivative Activity Volume Gas Derivatives [Member]
Number of Energy Contracts	767	[1]
Dths	106,730,705	[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.