Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) - Power [Member] $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) Counterparty
Derivative [Line Items]
Current Exposure	$ 340
Securities held as Collateral	12
Net exposure	328
Number of Counterparties greater than 10%	$ 1
Number Of Active Counterparties On Credit Risk Derivatives | Counterparty	142
Investment Grade - External Rating [Member]
Derivative [Line Items]
Percentage Of Credit Exposure	99.00%
Investment Grade [Member]
Derivative [Line Items]
Current Exposure	$ 337
Securities held as Collateral	12
Net exposure	325
Number of Counterparties greater than 10%	1
Amount Of Net Credit Exposure Greater Than Ten Percent	191	[1]
External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Current Exposure	3
Securities held as Collateral	0
Amount Of Net Credit Exposure Greater Than Ten Percent	0
Non-Investment Grade [Member]
Derivative [Line Items]
Net exposure	3
Number of Counterparties greater than 10%	0
Letter of Credit [Member]
Derivative [Line Items]
Securities held as Collateral	$ 12

[1] Represents net exposure with PSE&G.