Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended
	Mar. 31, 2013	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 31, 2011
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations				74.40%	32.10%	33.90%
Change in estimates and interest related to uncertain tax positions				$ 56
Establishment of valuation allowance on deferred tax assets	101
PCI Future Deferred Tax Asset	101
Income tax settlement with IRS					8	5
Additional state income tax expense						2
Federal and state net operating losses, years				20 years
Federal and state net operating losses, expiration period				2029 to 2032
Unrecognized tax benefits that would impact effective tax rate				9
Uncertain tax position Pre-tax interest income (expense) recognize				(125)	23	23
Uncertain tax position After-tax interest income (expense) recognized				(75)	14	14
Accrued interest receivable				2	10
Accrued interest payable						4
Estimated possible decrease in unrecognized tax benefit lower range				700
Estimated possible decrease in unrecognized tax benefit upper range				800
Other taxes for continuing operations				422	426	445
Valuation allowance for deferred tax assets	101			101
Delmarva Power & Light Co/De [Member]
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations				38.60%	37.60%	37.20%
Federal and state net operating losses, years				20 years
Federal and state net operating losses, expiration period				2029 to 2032
Unrecognized tax benefits that would impact effective tax rate				1
Uncertain tax position Pre-tax interest income (expense) recognize				1	1	6
Uncertain tax position After-tax interest income (expense) recognized						4
Accrued interest receivable				2	1	1
Estimated possible decrease in unrecognized tax benefit lower range				4
Estimated possible decrease in unrecognized tax benefit upper range				6
After-tax effect of revised lease rerun	377
Additional interest income	1
Additional income tax (expense) benefit after-tax		1				4
Valuation allowance for deferred tax assets				0	0
Delmarva Power & Light Co/De [Member] | Deposit Made in 2006 [Member]
Schedule of Income Tax [Line Items]
Additional income tax (expense) benefit after-tax						1
Potomac Electric Power Co [Member]
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations				34.50%	27.60%	26.70%
PCI Future Deferred Tax Asset							4
Income tax settlement with IRS				3	10	9
Federal and state net operating losses, years				20 years
Federal and state net operating losses, expiration period				2029 to 2032
Unrecognized tax benefits that would impact effective tax rate				1
Uncertain tax position Pre-tax interest income (expense) recognize				5	18	8
Uncertain tax position After-tax interest income (expense) recognized				3	11	5
Accrued interest receivable				9	5
Accrued interest payable						6
Estimated possible decrease in unrecognized tax benefit lower range				65
Estimated possible decrease in unrecognized tax benefit upper range				85
Additional interest income	5			5
Additional income tax (expense) benefit after-tax		1	5
Reversal of federal tax benefits						23
Reversal of accrued state interest receivable						1
Receipt of refunds							5
Valuation allowance for deferred tax assets				0	0
Amended state returns				20
Refunds received				4
Income tax remaining recoverable amount				16
After-tax effect of revised lease rerun	377
Atlantic City Electric Co [Member]
Schedule of Income Tax [Line Items]
Consolidated effective income tax rates from continuing operations				27.50%	34.00%	45.80%
Income tax settlement with IRS				9	1	5
Federal and state net operating losses, years				20 years
Federal and state net operating losses, expiration period				2029 to 2032
Unrecognized tax benefits that would impact effective tax rate				0
Uncertain tax position Pre-tax interest income (expense) recognize				12	2	(5)
Uncertain tax position After-tax interest income (expense) recognized				7	1	(3)
Accrued interest receivable				14	7	6
Estimated possible decrease in unrecognized tax benefit lower range				4
Estimated possible decrease in unrecognized tax benefit upper range				6
Additional interest income	6
Additional income tax (expense) benefit after-tax			1
Valuation allowance for deferred tax assets				0	0
Amended state returns				1
After-tax effect of revised lease rerun	377
Atlantic City Electric Co [Member] | Deposit Made in 2006 [Member]
Schedule of Income Tax [Line Items]
Additional income tax (expense) benefit after-tax		3
Interest Expense [Member] | Delmarva Power & Light Co/De [Member]
Schedule of Income Tax [Line Items]
After-tax effect of revised lease rerun	54
Interest Expense [Member] | Potomac Electric Power Co [Member]
Schedule of Income Tax [Line Items]
After-tax effect of revised lease rerun	54
Interest Expense [Member] | Atlantic City Electric Co [Member]
Schedule of Income Tax [Line Items]
After-tax effect of revised lease rerun	$ 54