Commitments And Contingent Liabilities (New Generation And Development) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012 project MW	Sep. 30, 2011
Long-term Purchase Commitment [Line Items]
Total expenditures to date	$ 1,969	$ 1,479
Estimated total cost of land and buildings owned phase	194
Number of MW of solar capacity placed into service	38
Number Of Solar Projects Placed Into Service	22
Energy Holdings-Solar [Member]
Long-term Purchase Commitment [Line Items]
Guarantee payment of obligations	72
Guarantee obligations outstanding	17
Energy Holdings-Solar [Member] | DELAWARE
Long-term Purchase Commitment [Line Items]
Guarantee payment of obligations	37
Sites acquired during period, MW	15
Estimated project costs	47
Energy Holdings-Solar [Member] | ARIZONA
Long-term Purchase Commitment [Line Items]
Sites acquired during period, MW	25
Estimated project costs	75
Power [Member]
Long-term Purchase Commitment [Line Items]
Total expenditures to date	493	530
Power [Member] | Nuclear Steam Path Capital Additions [Member]
Long-term Purchase Commitment [Line Items]
Approximate amount committed	192
Total expenditures to date	138
Power [Member] | Nuclear Up Rate Capital Additions [Member] | Peach Bottom Units [Member]
Long-term Purchase Commitment [Line Items]
Approximate amount committed	419
Increase of MW nominal capacity after completion of upgrades	130
Total expenditures to date	56
Power [Member] | Connecticut Capital Additions [Member]
Long-term Purchase Commitment [Line Items]
Number of MW of gas fired peaking capacity to be built	130
Long term purchase commitment amount low range	150
Power [Member] | PJM Interconnection Capital Additions [Member]
Long-term Purchase Commitment [Line Items]
Total expenditures to date	247
Power [Member] | PJM Interconnection Capital Additions [Member] | Period 2013-2015 [Member]
Long-term Purchase Commitment [Line Items]
Number of MW of gas fired peaking capacity to be built	267
PSE And G [Member]
Long-term Purchase Commitment [Line Items]
Total expenditures to date	1,369	939
Number of MW of solar generation on existing utility poles being installed	40
Total project cost	249
Number of MW of installation of solar generation on land and building	40
PSE And G [Member] | Solar Capital Additions [Member]
Long-term Purchase Commitment [Line Items]
Total expenditures to date	232
Investment in projects, amount	$ 190
Remedial Investigation And Feasibility Study [Member]
Long-term Purchase Commitment [Line Items]
Approximately amount of MW's already installed	33