Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) - Power [Member] $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Counterparty
Derivative [Line Items]
Current Exposure	$ 488
Collateral held from counterparties	176
Net Credit Exposure With Counterparties After Applying Collateral	312
Number of Counterparties greater than 10%	1
Net Exposure of Counterparties greater than 10%	$ 160
Number of active counterparties on credit risk derivatives | Counterparty	133
Investment Grade - External Rating [Member]
Derivative [Line Items]
Credit exposure, percentage	92.00%
Current Exposure	$ 451
Collateral held from counterparties	175
Net Credit Exposure With Counterparties After Applying Collateral	276
Number of Counterparties greater than 10%	1
Net Exposure of Counterparties greater than 10%	160	[1]
Non-Investment Grade - External Rating [Member]
Derivative [Line Items]
Current Exposure	24
Collateral held from counterparties	0
Net Credit Exposure With Counterparties After Applying Collateral	24
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	12
Collateral held from counterparties	1
Net Credit Exposure With Counterparties After Applying Collateral	11
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	1
Collateral held from counterparties	0
Net Credit Exposure With Counterparties After Applying Collateral	1
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	0
Cash [Member]
Derivative [Line Items]
Collateral held from counterparties	14
Letter of Credit [Member]
Derivative [Line Items]
Collateral held from counterparties	$ 162

[1] Represents net exposure with PSE&G.