Financial Risk Management Activities (Schedule Providing Credit Risk From Others, Net Of Collateral) (Detail) - Power [Member] $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Counterparty
Derivative [Line Items]
Current Exposure	$ 449
Collateral held from counterparties	95
Net Credit Exposure With Counterparties After Applying Collateral	354
Number of Counterparties greater than 10%	1
Net Exposure of Counterparties greater than 10%	$ 219
Number of active counterparties on credit risk derivatives | Counterparty	149
Investment Grade External Rating [Member]
Derivative [Line Items]
Credit exposure, percentage	93.00%
Investment Grade [Member]
Derivative [Line Items]
Current Exposure	$ 423
Collateral held from counterparties	94
Net Credit Exposure With Counterparties After Applying Collateral	329
Number of Counterparties greater than 10%	1
Net Exposure of Counterparties greater than 10%	219	[1]
Non-Investment Grade [Member]
Derivative [Line Items]
Current Exposure	26
Collateral held from counterparties	1
Net Credit Exposure With Counterparties After Applying Collateral	25
Number of Counterparties greater than 10%	0
Net Exposure of Counterparties greater than 10%	0
Cash [Member]
Derivative [Line Items]
Collateral held from counterparties	1
Letter of Credit [Member]
Derivative [Line Items]
Collateral held from counterparties	$ 94

[1] Represents net exposure with PSE&G.