Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended									0 Months Ended	12 Months Ended									12 Months Ended
	Nov. 02, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013 Adjustment [Member]	Dec. 31, 2012 Adjustment [Member]	Dec. 31, 2011 Adjustment [Member]	Dec. 31, 2010 Adjustment [Member]	Dec. 31, 2012 Time-Based Restricted Stock [Member]	Dec. 31, 2011 Pepco Energy Services [Member]	Dec. 31, 2013 Asset Removal Costs [Member]	Dec. 31, 2012 Asset Removal Costs [Member]	Dec. 31, 2013 Potomac Electric Power Co [Member]	Dec. 31, 2012 Potomac Electric Power Co [Member]	Dec. 31, 2011 Potomac Electric Power Co [Member]	Dec. 31, 2010 Potomac Electric Power Co [Member]	Dec. 31, 2013 Potomac Electric Power Co [Member] Transmission and Distribution [Member]	Dec. 31, 2012 Potomac Electric Power Co [Member] Transmission and Distribution [Member]	Dec. 31, 2011 Potomac Electric Power Co [Member] Transmission and Distribution [Member]	Dec. 31, 2013 Potomac Electric Power Co [Member] Asset Removal Costs [Member]	Dec. 31, 2012 Potomac Electric Power Co [Member] Asset Removal Costs [Member]	Nov. 02, 2013 Delmarva Power & Light Co/De [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Delmarva Power & Light Co/De [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Transmission and Distribution [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Transmission and Distribution [Member]	Dec. 31, 2011 Delmarva Power & Light Co/De [Member] Transmission and Distribution [Member]	Dec. 31, 2010 Delmarva Power & Light Co/De [Member] Transmission and Distribution [Member]	Dec. 31, 2013 Delmarva Power & Light Co/De [Member] Asset Removal Costs [Member]	Dec. 31, 2012 Delmarva Power & Light Co/De [Member] Asset Removal Costs [Member]	Dec. 31, 2013 Atlantic City Electric Co [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member]	Dec. 31, 2011 Atlantic City Electric Co [Member]	Dec. 31, 2010 Atlantic City Electric Co [Member]	Dec. 31, 2013 Atlantic City Electric Co [Member] Transmission and Distribution [Member]	Dec. 31, 2012 Atlantic City Electric Co [Member] Transmission and Distribution [Member]	Dec. 31, 2011 Atlantic City Electric Co [Member] Transmission and Distribution [Member]	Dec. 31, 2013 Atlantic City Electric Co [Member] Minimum [Member]
Significant Accounting Policies [Line Items]
Unbilled revenue		$ 177	$ 182											$ 80	$ 81									$ 61	$ 62								$ 36	$ 39
Taxes included in gross revenues		346	356	378										318	324	338								17	15	18							11	15	22
Restricted stock awards vesting period										3 years
Estimated fair value of an asset	Greater than 50%																						Greater than 50%
Awards received from the U.S. DOE																	149																			19
AFUDC for borrowed funds		7	7	11										5	4	8								2	2	1								1	2					1
AFUDC for equity component		11	14	15										9	8	12								2	3	3								3	1					1
Regulatory Liabilities												275	324								102	122									173	202
Number of subsidiaries, allocated		3
Increase in income tax expense after adjustments		4		2										4
Tax amount of derivative loss occurred due to discontinued operation											1
Adjustment																									1
Reclassification adjustment																										11
Increase of deferred electric service cost																																		3
Deferred income tax liabilities						32
Annual Depreciation Rate																		2.20%	2.50%	2.60%							2.60%	2.70%	2.80%	2.80%							2.80%	3.00%	3.00%
Preferred stock, shares outstanding														0										0
Retained earnings		595	1,077	1,040	1,027		(32)	(32)	(32)					992	888									637	578								190	200
Reclassification adjustment relating to uncertain tax positions																$ 1																			$ 1
Unbilled receivables billing period		1 year
Securitization debt capitalization rate																																	30.00%