Regulatory Matters (Schedule Of Regulatory Assets And Regulatory Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	$ 2,614		$ 2,196
Regulatory Liabilities	501		526
Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	487		299
Regulatory Liabilities	141		169
Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	694		662
Regulatory Liabilities	102		60
Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	288		227
Regulatory Liabilities	258		297
Asset Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	324		388
Asset Removal Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	122		144
Asset Removal Costs [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	202		244
Other [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	43		31
Other [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	19		25
Other [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	5		4
Other [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	12		3
Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	78		33
Deferred Energy Supply Costs [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	62		11
Deferred Energy Supply Costs [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	6		12
Excess Depreciation Reserve [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	11		26
Excess Depreciation Reserve [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	11		26
AOC SOCAs[Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	8
Smart Grid [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	229	[1]	142	[1]
Smart Grid [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	159	[1]	96	[1]
Smart Grid [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	70	[2]	46	[2]
Recoverable Income Taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	177		145
Recoverable Income Taxes [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	75		57
Recoverable Income Taxes [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	33		27
Recoverable Income Taxes [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	69		61
MAPP Abandonment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	88	[1]
MAPP Abandonment Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	50	[1]
MAPP Abandonment Costs [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	38	[2]
Demand Side Management Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	45		20
Incremental Storm Restoration Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	89		28
Incremental Storm Restoration Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	44		14
Incremental Storm Restoration Costs [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	34		8
Incremental Storm Restoration Costs [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	11		6
Recoverable Workers Compensation And Long-Term Disability Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	31		34
Recoverable Workers Compensation And Long-Term Disability Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	31		34
Deferred Debt Extinguishment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	53	[1]	57	[1]
Deferred Debt Extinguishment Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	28	[1]	30	[1]
Deferred Debt Extinguishment Costs [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	15	[2]	16	[2]
Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	183	[1]	126	[1]
Deferred Energy Supply Costs [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	4		4
Deferred Energy Supply Costs [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	166	[1]	105	[1]
Deferred Energy Supply Costs [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	13	[3]	16	[3]
Other Regulatory Assets [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	173		129
Other Regulatory Assets [Member] | Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	51		44
Other Regulatory Assets [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	34		41
Other Regulatory Assets [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	42		35
Securitized Stranded Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	416	[1]	481	[1]
Securitized Stranded Costs [Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	416	[1]	481	[1]
Regulatory Liabilities	16		19
AOC SOCAs[Member] | Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	11
Pension And OPEB Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	1,171	[1]	1,037	[1]
Deferred Losses On Gas Derivatives [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	4		17
Deferred Losses On Gas Derivatives [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	4		17
Deferred Income Taxes Due to Customers [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	45		48
Deferred Income Taxes Due to Customers [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	38		38
COPCO Acquisition Adjustment [Member] | Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	$ 26	[2]	$ 30	[2]

[1] A return is generally earned on these deferrals.

[2] A return is earned on these deferrals.

[3] A return is generally earned in Delaware on this deferral.