Property, Plant And Equipment (Schedule Of Property Plant And Equipment) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	$ 13,625	$ 12,855
Accumulated Depreciation	4,779	4,635
Net Book Value	8,846	8,220
Distribution [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	8,320	7,832
Accumulated Depreciation	2,954	2,848
Net Book Value	5,366	4,984
Transmission [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	2,783	2,462
Accumulated Depreciation	866	834
Net Book Value	1,917	1,628
Gas [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	458	429
Accumulated Depreciation	137	133
Net Book Value	321	296
Construction Work In Progress [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	692	742
Net Book Value	692	742
Non-Operating And Other Property [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	1,265	1,282
Accumulated Depreciation	725	738
Net Book Value	540	544
Generation [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	107	108
Accumulated Depreciation	97	82
Net Book Value	10	26
Delmarva Power & Light Co/De [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	3,422	3,188
Accumulated Depreciation	1,000	926
Net Book Value	2,422	2,262
Delmarva Power & Light Co/De [Member] | Distribution [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	1,664	1,580
Accumulated Depreciation	498	435
Net Book Value	1,166	1,145
Delmarva Power & Light Co/De [Member] | Transmission [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	877	788
Accumulated Depreciation	233	230
Net Book Value	644	558
Delmarva Power & Light Co/De [Member] | Gas [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	458	429
Accumulated Depreciation	137	133
Net Book Value	321	296
Delmarva Power & Light Co/De [Member] | Construction Work In Progress [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	206	151
Accumulated Depreciation
Net Book Value	206	151
Delmarva Power & Light Co/De [Member] | Non-Operating And Other Property [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	217	240
Accumulated Depreciation	132	128
Net Book Value	85	112
Atlantic City Electric Co [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	2,771	2,548
Accumulated Depreciation	787	766
Net Book Value	1,984	1,782
Atlantic City Electric Co [Member] | Distribution [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	1,707	1,591
Accumulated Depreciation	461	453
Net Book Value	1,246	1,138
Atlantic City Electric Co [Member] | Transmission [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	740	688
Accumulated Depreciation	214	206
Net Book Value	526	482
Atlantic City Electric Co [Member] | Construction Work In Progress [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	133	87
Accumulated Depreciation
Net Book Value	133	87
Atlantic City Electric Co [Member] | Non-Operating And Other Property [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	181	172
Accumulated Depreciation	103	98
Net Book Value	78	74
Atlantic City Electric Co [Member] | Generation [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	10	10
Accumulated Depreciation	9	9
Net Book Value	1	1
Potomac Electric Power Co [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	6,850	6,578
Accumulated Depreciation	2,705	2,704
Net Book Value	4,145	3,874
Potomac Electric Power Co [Member] | Distribution [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	4,949	4,661
Accumulated Depreciation	1,995	1,960
Net Book Value	2,954	2,701
Potomac Electric Power Co [Member] | Transmission [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	1,166	986
Accumulated Depreciation	419	398
Net Book Value	747	588
Potomac Electric Power Co [Member] | Construction Work In Progress [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	303	438
Accumulated Depreciation
Net Book Value	303	438
Potomac Electric Power Co [Member] | Non-Operating And Other Property [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]
Original Cost	432	493
Accumulated Depreciation	291	346
Net Book Value	$ 141	$ 147