Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) - Power [Member] $ in Millions	Sep. 30, 2017 USD ($) Counterparty
Derivative [Line Items]
Current Exposure	$ 323
Securities held as Collateral	56
Net exposure	267
Number of Counterparties greater than 10%	2
Amount Of Net Credit Exposure Greater Than Ten Percent	$ 97
Number Of Active Counterparties On Credit Risk Derivatives | Counterparty	144
Investment Grade [Member]
Derivative [Line Items]
Current Exposure	$ 318
Securities held as Collateral	55
Net exposure	263
Number of Counterparties greater than 10%	2
Amount Of Net Credit Exposure Greater Than Ten Percent	128	[1]
Non-Investment Grade [Member]
Derivative [Line Items]
Current Exposure	5
Securities held as Collateral	1
Net exposure	4
Number of Counterparties greater than 10%	0
Amount Of Net Credit Exposure Greater Than Ten Percent	0
Cash [Member]
Derivative [Line Items]
Securities held as Collateral	3
Letter of Credit [Member]
Derivative [Line Items]
Securities held as Collateral	$ 53

[1] net exposure of $97 million with PSE&G.