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		Dec. 31, 2016	Dec. 31, 2015
Derivatives And Hedging Activities [Abstract]
Derivatives in a liability position with credit risk-related contingencies that are not fully collateralized		$ (24)	$ (2)
Related derivatives in an asset position		19	0
Collateral posting in the normal course of business related to these derivatives		4	0
Net position of derivative contracts/additional collateral posting requirements	[1]	$ (1)	$ (2)

[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.