Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) (Power [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Derivative [Line Items]
Current Exposure	$ 413
Securities held as Collateral	96
Net exposure	405
Number of Counterparties greater than 10%	1
Amount Of Net Credit Exposure Greater Than Ten Percent	197
Investment Grade - External Rating [Member]
Derivative [Line Items]
Current Exposure	396
Securities held as Collateral	96
Net exposure	388
Number of Counterparties greater than 10%	1
Amount Of Net Credit Exposure Greater Than Ten Percent	197	[1]
Non-Investment Grade - External Rating [Member]
Derivative [Line Items]
Current Exposure	2
Securities held as Collateral	0
Net exposure	2
Number of Counterparties greater than 10%	0
Amount Of Net Credit Exposure Greater Than Ten Percent	0
Investment Grade - No External Rating [Member]
Derivative [Line Items]
Current Exposure	4
Securities held as Collateral	0
Net exposure	4
Number of Counterparties greater than 10%	0
Amount Of Net Credit Exposure Greater Than Ten Percent	0
Non-Investment Grade - No External Rating [Member]
Derivative [Line Items]
Current Exposure	11
Securities held as Collateral	0
Net exposure	11
Number of Counterparties greater than 10%	0
Amount Of Net Credit Exposure Greater Than Ten Percent	$ 0

[1] Represents net exposure with PSE&G.