Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) (Power [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Derivative [Line Items]
Current Exposure	$ 197
Securities held as Collateral	17
Net exposure	197
Number of Counterparties greater than 10%	1
Net Exposure of Counterparties greater than 10%	90
Investment Grade - External Rating [Member]
Derivative [Line Items]
Current Exposure	180
Securities held as Collateral	17
Net exposure	180
Number of Counterparties greater than 10%	1
Net Exposure of Counterparties greater than 10%	90	[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
Net Exposure of Counterparties greater than 10%	0
Investment Grade - No External Rating [Member]
Derivative [Line Items]
Current Exposure	7
Securities held as Collateral	0
Net exposure	7
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	0
Non-Investment Grade - No External Rating [Member]
Derivative [Line Items]
Current Exposure	8
Securities held as Collateral	0
Net exposure	8
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	$ 0

[1] Represents net exposure with PSE&G.