Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Original Cost	$ 14,567	$ 13,625
Accumulated Depreciation	4,863	4,779
Net Book Value	9,704	8,846
Generation [Member]
Property, Plant and Equipment [Line Items]
Original Cost	105	107
Accumulated Depreciation	99	97
Net Book Value	6	10
Distribution [Member]
Property, Plant and Equipment [Line Items]
Original Cost	8,896	8,320
Accumulated Depreciation	2,961	2,954
Net Book Value	5,935	5,366
Transmission [Member]
Property, Plant and Equipment [Line Items]
Original Cost	2,991	2,783
Accumulated Depreciation	908	866
Net Book Value	2,083	1,917
Gas [Member]
Property, Plant and Equipment [Line Items]
Original Cost	481	458
Accumulated Depreciation	142	137
Net Book Value	339	321
Construction Work In Progress [Member]
Property, Plant and Equipment [Line Items]
Original Cost	677	692
Accumulated Depreciation
Net Book Value	677	692
Non-Operating and Other Property [Member]
Property, Plant and Equipment [Line Items]
Original Cost	1,417	1,265
Accumulated Depreciation	753	725
Net Book Value	664	540
Potomac Electric Power Co [Member]
Property, Plant and Equipment [Line Items]
Original Cost	7,310	6,850
Accumulated Depreciation	2,772	2,705
Net Book Value	4,538	4,145
Potomac Electric Power Co [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Original Cost	5,287	4,949
Accumulated Depreciation	2,027	1,995
Net Book Value	3,260	2,954
Potomac Electric Power Co [Member] | Transmission [Member]
Property, Plant and Equipment [Line Items]
Original Cost	1,223	1,166
Accumulated Depreciation	444	419
Net Book Value	779	747
Potomac Electric Power Co [Member] | Construction Work In Progress [Member]
Property, Plant and Equipment [Line Items]
Original Cost	312	303
Accumulated Depreciation
Net Book Value	312	303
Potomac Electric Power Co [Member] | Non-Operating and Other Property [Member]
Property, Plant and Equipment [Line Items]
Original Cost	488	432
Accumulated Depreciation	301	291
Net Book Value	187	141
Delmarva Power & Light Co/De [Member]
Property, Plant and Equipment [Line Items]
Original Cost	3,673	3,422
Accumulated Depreciation	1,016	1,000
Net Book Value	2,657	2,422
Delmarva Power & Light Co/De [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Original Cost	1,788	1,664
Accumulated Depreciation	492	498
Net Book Value	1,296	1,166
Delmarva Power & Light Co/De [Member] | Transmission [Member]
Property, Plant and Equipment [Line Items]
Original Cost	982	877
Accumulated Depreciation	243	233
Net Book Value	739	644
Delmarva Power & Light Co/De [Member] | Gas [Member]
Property, Plant and Equipment [Line Items]
Original Cost	481	458
Accumulated Depreciation	142	137
Net Book Value	339	321
Delmarva Power & Light Co/De [Member] | Construction Work In Progress [Member]
Property, Plant and Equipment [Line Items]
Original Cost	158	206
Accumulated Depreciation
Net Book Value	158	206
Delmarva Power & Light Co/De [Member] | Non-Operating and Other Property [Member]
Property, Plant and Equipment [Line Items]
Original Cost	264	217
Accumulated Depreciation	139	132
Net Book Value	125	85
Atlantic City Electric Co [Member]
Property, Plant and Equipment [Line Items]
Original Cost	2,901	2,771
Accumulated Depreciation	751	787
Net Book Value	2,150	1,984
Atlantic City Electric Co [Member] | Generation [Member]
Property, Plant and Equipment [Line Items]
Original Cost	10	10
Accumulated Depreciation	9	9
Net Book Value	1	1
Atlantic City Electric Co [Member] | Distribution [Member]
Property, Plant and Equipment [Line Items]
Original Cost	1,821	1,707
Accumulated Depreciation	442	461
Net Book Value	1,379	1,246
Atlantic City Electric Co [Member] | Transmission [Member]
Property, Plant and Equipment [Line Items]
Original Cost	786	740
Accumulated Depreciation	221	214
Net Book Value	565	526
Atlantic City Electric Co [Member] | Construction Work In Progress [Member]
Property, Plant and Equipment [Line Items]
Original Cost	110	133
Accumulated Depreciation
Net Book Value	110	133
Atlantic City Electric Co [Member] | Non-Operating and Other Property [Member]
Property, Plant and Equipment [Line Items]
Original Cost	174	181
Accumulated Depreciation	79	103
Net Book Value	$ 95	$ 78