Derivatives And Hedging Activities (Additional Cash Collateral The Utility Would Be Required To Post If Its Credit-Risk-Related Contingency Features Were Triggered) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Derivatives And Hedging Activities [Abstract]
Derivatives in a liability position with credit risk-related contingencies that are not fully collateralized	$ (611)
Related derivatives in an asset position	86
Collateral posting in the normal course of business related to these derivatives	250
Net position of derivative contracts/additional collateral posting requirements	$ (275)	[1]

[1] This calculation excludes the impact of closed but unpaid positions, as their settlement is not impacted by any of the Utility's credit risk-related contingencies.