Regulatory Matters - Schedule of Regulatory Assets and Regulatory Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	$ 2,087	$ 2,614
Regulatory Liabilities	399	501
Pension and OPEB Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	667	1,171
Securitized Stranded Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	350	416
Smart Grid Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	251	230
Recoverable Income Taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	225	177
Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	136	183
Demand-Side Management Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	125	57
Incremental Storm Restoration Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	72	89
MAPP Abandonment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	68	88
Deferred Debt Extinguishment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	47	53
Recoverable Workers' Compensation and Long-Term Disability Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	26	31
Deferred Losses on Gas Derivatives [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets		4
Other Regulatory Assets [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	120	115
Asset Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	275	324
Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	46	78
Deferred Income Taxes Due to Customers [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	45	45
Deferred Gains on Gas Derivatives [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	1
Excess Depreciation Reserve [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities		11
Other Regulatory Liabilities [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	32	43
Potomac Electric Power Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	563	487
Regulatory Liabilities	113	141
Potomac Electric Power Co [Member] | Smart Grid Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	168	159
Potomac Electric Power Co [Member] | Recoverable Income Taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	107	75
Potomac Electric Power Co [Member] | Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	6	4
Potomac Electric Power Co [Member] | Demand-Side Management Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	98	45
Potomac Electric Power Co [Member] | Incremental Storm Restoration Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	37	44
Potomac Electric Power Co [Member] | MAPP Abandonment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	37	50
Potomac Electric Power Co [Member] | Deferred Debt Extinguishment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	25	28
Potomac Electric Power Co [Member] | Recoverable Workers' Compensation and Long-Term Disability Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	26	31
Potomac Electric Power Co [Member] | Other Regulatory Assets [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	59	51
Potomac Electric Power Co [Member] | Asset Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	102	122
Potomac Electric Power Co [Member] | Other Regulatory Liabilities [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	11	19
Delmarva Power & Light Co/De [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	311	288
Regulatory Liabilities	229	258
Delmarva Power & Light Co/De [Member] | Smart Grid Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	83	71
Delmarva Power & Light Co/De [Member] | Recoverable Income Taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	76	69
Delmarva Power & Light Co/De [Member] | Demand-Side Management Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	27	12
Delmarva Power & Light Co/De [Member] | Incremental Storm Restoration Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	9	11
Delmarva Power & Light Co/De [Member] | MAPP Abandonment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	31	38
Delmarva Power & Light Co/De [Member] | Deferred Debt Extinguishment Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	13	15
Delmarva Power & Light Co/De [Member] | Deferred Losses on Gas Derivatives [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets		4
Delmarva Power & Light Co/De [Member] | Other Regulatory Assets [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	37	29
Delmarva Power & Light Co/De [Member] | COPCO Acquisition Adjustment [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	22	26
Delmarva Power & Light Co/De [Member] | Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	13	13
Delmarva Power & Light Co/De [Member] | Asset Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	173	202
Delmarva Power & Light Co/De [Member] | Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	3	6
Delmarva Power & Light Co/De [Member] | Deferred Income Taxes Due to Customers [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	37	38
Delmarva Power & Light Co/De [Member] | Other Regulatory Liabilities [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	15	12
Delmarva Power & Light Co/De [Member] | Deferred Gains on Gas Derivative [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	1
Atlantic City Electric Co [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	569	694
Regulatory Liabilities	57	102
Atlantic City Electric Co [Member] | Securitized Stranded Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	350	416
Atlantic City Electric Co [Member] | Recoverable Income Taxes [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	42	33
Atlantic City Electric Co [Member] | Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	117	166
Atlantic City Electric Co [Member] | Incremental Storm Restoration Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	26	34
Atlantic City Electric Co [Member] | Other Regulatory Assets [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets	34	34
Atlantic City Electric Co [Member] | ACE SOCAs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory assets		11
Atlantic City Electric Co [Member] | Deferred Energy Supply Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	38	62
Atlantic City Electric Co [Member] | Excess Depreciation Reserve [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities		11
Atlantic City Electric Co [Member] | Other Regulatory Liabilities [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	6	5
Atlantic City Electric Co [Member] | Federal and State Tax Benefits, Related to Securitized Stranded Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities	13	16
Atlantic City Electric Co [Member] | ACE SOCAs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Liabilities		$ 8