Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Power [Member]
Derivative [Line Items]
Current Exposure	$ 323
Securities held as Collateral	85
Net exposure	321
Number of Counterparties greater than 10%	2
Net Exposure of Counterparties greater than 10%	153
Power [Member] | Investment Grade - External Rating [Member]
Derivative [Line Items]
Current Exposure	311
Securities held as Collateral	85
Net exposure	309
Number of Counterparties greater than 10%	2
Net Exposure of Counterparties greater than 10%	153	[1]
Power [Member] | Non-Investment Grade - External Rating [Member]
Derivative [Line Items]
Current Exposure	3
Securities held as Collateral	0
Net exposure	3
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	0
Power [Member] | Investment Grade - No External Rating [Member]
Derivative [Line Items]
Current Exposure	9
Securities held as Collateral	0
Net exposure	9
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	0
Power [Member] | Non-Investment Grade - No External Rating [Member]
Derivative [Line Items]
Current Exposure	0
Securities held as Collateral	0
Net exposure	0
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	0
PSE And G [Member]
Derivative [Line Items]
Net exposure	108
Nonaffiliated [Member]
Derivative [Line Items]
Net exposure	$ 45

[1] Includes net exposure of $108 million with PSE&G. The remaining net exposure of $45 million is with one nonaffiliated power purchaser which is a regulated investment grade counterparty.