Debt - Components of Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt instrument, carrying value	$ 906	$ 906
Debt instrument, carrying value	906	906
Total long-term debt	4,470	4,190
Net unamortized discount	(14)	(13)
Current portion of long-term debt	(403)	(529)
Total net long-term debt	4,053	3,648
Total long-term debt	4,470	4,190
Current portion of long-term debt	(403)	(529)
First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	3,321	3,140
Debt instrument, carrying value	3,321	3,140
Medium-Term Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	40	40
Debt instrument, carrying value	40	40
Potomac Electric Power Co [Member]
Debt Instrument [Line Items]
Total long-term debt	1,910	1,710
Net unamortized discount	(11)	(9)
Current portion of long-term debt	(175)	(200)
Total net long-term debt	1,724	1,501
Total long-term debt	1,910	1,710
Current portion of long-term debt	(175)	(200)
Atlantic City Electric Co [Member]
Debt Instrument [Line Items]
Total long-term debt	861	830
Net unamortized discount	(1)	(1)
Current portion of long-term debt	(107)	(69)
Total net long-term debt	753	760
Total long-term debt	861	830
Current portion of long-term debt	(107)	(69)
Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Total long-term debt	761	830
Total long-term debt	761	830
Atlantic City Electric Co [Member] | Variable Rate Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	100
Debt instrument maturity date	2014
Debt instrument, carrying value	100
Debt instrument maturity date	2014
Atlantic City Electric Co [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Total long-term debt	255	295
Net unamortized discount	0
Current portion of long-term debt	(41)	(39)
Total Net Long-Term Debt	214	256
Total long-term debt	255	295
Current portion of long-term debt	(41)	(39)
Total net long-term debt	214	256
Delmarva Power & Light Co/De [Member]
Debt Instrument [Line Items]
Total long-term debt	968	918
Net unamortized discount	(1)	(1)
Current portion of long-term debt	(100)	(250)
Total net long-term debt	867	667
Total long-term debt	968	918
Current portion of long-term debt	(100)	(250)
Delmarva Power & Light Co/De [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	650	600
Debt instrument, carrying value	650	600
Delmarva Power & Light Co/De [Member] | Unsecured Tax-Exempt Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	78	78
Debt instrument, carrying value	78	78
Delmarva Power & Light Co/De [Member] | Medium-Term Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	40	40
Debt instrument, carrying value	40	40
Delmarva Power & Light Co/De [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	200	200
Debt instrument, carrying value	200	200
4.95% Due 2013 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value		200
Debt interest percentage	4.95%
Debt instrument maturity date	2013
Debt instrument, carrying value		200
Debt interest percentage	4.95%
Debt instrument maturity date	2013
4.95% Due 2013 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value		200
Debt interest percentage	4.95%
Debt instrument maturity date	2013
Debt instrument, carrying value		200
Debt interest percentage	4.95%
Debt instrument maturity date	2013
4.65% Due 2014 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	175	175
Debt interest percentage	4.65%
Debt instrument maturity date	2014
Debt instrument, carrying value	175	175
Debt interest percentage	4.65%
Debt instrument maturity date	2014
4.65% Due 2014 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	175	175
Debt interest percentage	4.65%
Debt instrument maturity date	2014
Debt instrument, carrying value	175	175
Debt interest percentage	4.65%
Debt instrument maturity date	2014
3.05% Due 2022 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	200	200
Debt interest percentage	3.05%
Debt instrument maturity date	2022
Debt instrument, carrying value	200	200
Debt interest percentage	3.05%
Debt instrument maturity date	2022
3.05% Due 2022 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	200	200
Debt interest percentage	3.05%
Debt instrument maturity date	2022
Debt instrument, carrying value	200	200
Debt interest percentage	3.05%
Debt instrument maturity date	2022
6.20% Due 2022 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	110	110
Debt interest percentage	6.20%
Debt instrument maturity date	2022
Debt instrument, carrying value	110	110
Debt interest percentage	6.20%
Debt instrument maturity date	2022
6.20% Due 2022 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	110	110
Debt interest percentage	6.20%
Debt instrument maturity date	2022
Debt instrument, carrying value	110	110
Debt interest percentage	6.20%
Debt instrument maturity date	2022
5.75% Due 2034 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	100	100
Debt interest percentage	5.75%
Debt instrument maturity date	2034
Debt instrument, carrying value	100	100
Debt interest percentage	5.75%
Debt instrument maturity date	2034
5.75% Due 2034 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	100	100
Debt interest percentage	5.75%
Debt instrument maturity date	2034
Debt instrument, carrying value	100	100
Debt interest percentage	5.75%
Debt instrument maturity date	2034
5.40% Due 2035 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	175	175
Debt interest percentage	5.40%
Debt instrument maturity date	2035
Debt instrument, carrying value	175	175
Debt interest percentage	5.40%
Debt instrument maturity date	2035
5.40% Due 2035 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	175	175
Debt interest percentage	5.40%
Debt instrument maturity date	2035
Debt instrument, carrying value	175	175
Debt interest percentage	5.40%
Debt instrument maturity date	2035
6.50% Due 2037 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	500	500
Debt interest percentage	6.50%
Debt instrument maturity date	2037
Debt instrument, carrying value	500	500
Debt interest percentage	6.50%
Debt instrument maturity date	2037
6.50% Due 2037 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	500	500
Debt interest percentage	6.50%
Debt instrument maturity date	2037
Debt instrument, carrying value	500	500
Debt interest percentage	6.50%
Debt instrument maturity date	2037
7.90% Due 2038 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250	250
Debt interest percentage	7.90%
Debt instrument maturity date	2038
Debt instrument, carrying value	250	250
Debt interest percentage	7.90%
Debt instrument maturity date	2038
7.90% Due 2038 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250	250
Debt interest percentage	7.90%
Debt instrument maturity date	2038
Debt instrument, carrying value	250	250
Debt interest percentage	7.90%
Debt instrument maturity date	2038
4.15% Due 2043 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250
Debt interest percentage	4.15%
Debt instrument maturity date	2043
Debt instrument, carrying value	250
Debt interest percentage	4.15%
Debt instrument maturity date	2043
4.15% Due 2043 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250
Debt interest percentage	4.15%
Debt instrument maturity date	2043
Debt instrument, carrying value	250
Debt interest percentage	4.15%
Debt instrument maturity date	2043
4.95% Due 2043 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	150
Debt interest percentage	4.95%
Debt instrument maturity date	2043
Debt instrument, carrying value	150
Debt interest percentage	4.95%
Debt instrument maturity date	2043
4.95% Due 2043 [Member] | Potomac Electric Power Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	150
Debt interest percentage	4.95%
Debt instrument maturity date	2043
Debt instrument, carrying value	150
Debt interest percentage	4.95%
Debt instrument maturity date	2043
6.63% Due 2013 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value		69
Debt interest percentage	6.63%
Debt instrument maturity date	2013
Debt instrument, carrying value		69
Debt interest percentage	6.63%
Debt instrument maturity date	2013
7.63% Due 2014 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	7	7
Debt interest percentage	7.63%
Debt instrument maturity date	2014
Debt instrument, carrying value	7	7
Debt interest percentage	7.63%
Debt instrument maturity date	2014
7.68% Due 2015 - 2016 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	17	17
Debt interest percentage	7.68%
Debt instrument maturity date, start	2015
Debt instrument, carrying value	17	17
Debt instrument maturity date, end	2016
Debt interest percentage	7.68%
Debt instrument maturity date, start	2015
Debt instrument maturity date, end	2016
7.75% Due 2018 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250	250
Debt interest percentage	7.75%
Debt instrument maturity date	2018
Debt instrument, carrying value	250	250
Debt interest percentage	7.75%
Debt instrument maturity date	2018
6.80% Due 2021 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	39	39
Debt interest percentage	6.80%
Debt instrument maturity date	2021
Debt instrument, carrying value	39	39
Debt interest percentage	6.80%
Debt instrument maturity date	2021
4.35% Due 2021 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	200	200
Debt interest percentage	4.35%
Debt instrument maturity date	2021
Debt instrument, carrying value	200	200
Debt interest percentage	4.35%
Debt instrument maturity date	2021
4.875% Due 2029 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	23	23
Debt interest percentage	4.875%
Debt instrument maturity date	2029
Debt instrument, carrying value	23	23
Debt interest percentage	4.875%
Debt instrument maturity date	2029
5.80% Due 2034 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	120	120
Debt interest percentage	5.80%
Debt instrument maturity date	2034
Debt instrument, carrying value	120	120
Debt interest percentage	5.80%
Debt instrument maturity date	2034
5.80% Due 2036 [Member] | Atlantic City Electric Co [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	105	105
Debt interest percentage	5.80%
Debt instrument maturity date	2036
Debt instrument, carrying value	105	105
Debt interest percentage	5.80%
Debt instrument maturity date	2036
6.40% Due 2013 [Member] | Delmarva Power & Light Co/De [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value		250
Debt interest percentage	6.40%
Debt instrument maturity date	2013
Debt instrument, carrying value		250
Debt interest percentage	6.40%
Debt instrument maturity date	2013
5.22% Due 2016 [Member] | Delmarva Power & Light Co/De [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	100	100
Debt interest percentage	5.22%
Debt instrument maturity date	2016
Debt instrument, carrying value	100	100
Debt interest percentage	5.22%
Debt instrument maturity date	2016
3.50% Due 2023 [Member] | Delmarva Power & Light Co/De [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	300
Debt interest percentage	3.50%
Debt instrument maturity date	2023
Debt instrument, carrying value	300
Debt interest percentage	3.50%
Debt instrument maturity date	2023
4.00% Due 2042 [Member] | Delmarva Power & Light Co/De [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250	250
Debt interest percentage	4.00%
Debt instrument maturity date	2042
Debt instrument, carrying value	250	250
Debt interest percentage	4.00%
Debt instrument maturity date	2042
5.40% Due 2031 [Member] | Delmarva Power & Light Co/De [Member] | Unsecured Tax-Exempt Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	78	78
Debt interest percentage	5.40%
Debt instrument maturity date	2031
Debt instrument, carrying value	78	78
Debt interest percentage	5.40%
Debt instrument maturity date	2031
7.56% - 7.58% Due 2017 [Member] | Delmarva Power & Light Co/De [Member] | Medium-Term Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	14	14
Debt instrument maturity date	2017
Debt instrument, carrying value	14	14
Debt instrument maturity date	2017
Debt instrument percentage, minimum	7.56%
Debt instrument percentage, maximum	7.58%
Debt instrument percentage, minimum	7.56%
Debt instrument percentage, maximum	7.58%
6.81% Due 2018 [Member] | Delmarva Power & Light Co/De [Member] | Medium-Term Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	4	4
Debt interest percentage	6.81%
Debt instrument maturity date	2018
Debt instrument, carrying value	4	4
Debt interest percentage	6.81%
Debt instrument maturity date	2018
7.61% Due 2019 [Member] | Delmarva Power & Light Co/De [Member] | Medium-Term Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	12	12
Debt interest percentage	7.61%
Debt instrument maturity date	2019
Debt instrument, carrying value	12	12
Debt interest percentage	7.61%
Debt instrument maturity date	2019
7.72% Due 2027 [Member] | Delmarva Power & Light Co/De [Member] | Medium-Term Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	10	10
Debt interest percentage	7.72%
Debt instrument maturity date	2027
Debt instrument, carrying value	10	10
Debt interest percentage	7.72%
Debt instrument maturity date	2027
6.59% - 6.69% Due 2014 [Member] | Potomac Capital Investment Corporation (PCI) [Member] | Recourse Debt [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	11	11
Debt instrument maturity date	2014
Debt instrument, carrying value	11	11
Debt instrument maturity date	2014
Debt instrument percentage, minimum	6.59%
Debt instrument percentage, maximum	6.69%
Debt instrument percentage, minimum	6.59%
Debt instrument percentage, maximum	6.69%
5.90% - 7.46% Due 2017-2024 [Member] | Potomac Capital Investment Corporation (PCI) [Member] | Secured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	14	15
Debt instrument maturity date, start	2017
Debt instrument, carrying value	14	15
Debt instrument maturity date, end	2024
Debt instrument percentage, minimum	5.90%
Debt instrument percentage, maximum	7.46%
Debt instrument percentage, minimum	5.90%
Debt instrument percentage, maximum	7.46%
Debt instrument maturity date, start	2017
Debt instrument maturity date, end	2024
2.70% Due 2015 [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	250	250
Debt interest percentage	2.70%
Debt instrument maturity date	2015
Debt instrument, carrying value	250	250
Debt interest percentage	2.70%
Debt instrument maturity date	2015
5.90% Due 2016 [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	190	190
Debt interest percentage	5.90%
Debt instrument maturity date	2016
Debt instrument, carrying value	190	190
Debt interest percentage	5.90%
Debt instrument maturity date	2016
6.125% Due 2017 [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	81	81
Debt interest percentage	6.125%
Debt instrument maturity date	2017
Debt instrument, carrying value	81	81
Debt interest percentage	6.125%
Debt instrument maturity date	2017
7.45% Due 2032 [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	185	185
Debt interest percentage	7.45%
Debt instrument maturity date	2032
Debt instrument, carrying value	185	185
Debt interest percentage	7.45%
Debt instrument maturity date	2032
5.00% Due 2014 [Member] | Delmarva Power & Light Co/De [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	100	100
Debt interest percentage	5.00%
Debt instrument maturity date	2014
Debt instrument, carrying value	100	100
Debt interest percentage	5.00%
Debt instrument maturity date	2014
5.00% Due 2015 [Member] | Delmarva Power & Light Co/De [Member] | Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	100	100
Debt interest percentage	5.00%
Debt instrument maturity date	2015
Debt instrument, carrying value	100	100
Debt interest percentage	5.00%
Debt instrument maturity date	2015
4.46% Due 2016 [Member] | Atlantic City Electric Co [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	8	19
Debt interest percentage	4.46%
Debt instrument maturity date	2016
Debt instrument, carrying value	8	19
Debt interest percentage	4.46%
Debt instrument maturity date	2016
4.91% Due 2017 [Member] | Atlantic City Electric Co [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	46	75
Debt interest percentage	4.91%
Debt instrument maturity date	2017
Debt instrument, carrying value	46	75
Debt interest percentage	4.91%
Debt instrument maturity date	2017
5.05% Due 2020 [Member] | Atlantic City Electric Co [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	54	54
Debt interest percentage	5.05%
Debt instrument maturity date	2020
Debt instrument, carrying value	54	54
Debt interest percentage	5.05%
Debt instrument maturity date	2020
5.55% Due 2023 [Member] | Atlantic City Electric Co [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value	147	147
Debt interest percentage	5.55%
Debt instrument maturity date	2023
Debt instrument, carrying value	$ 147	$ 147
Debt interest percentage	5.55%
Debt instrument maturity date	2023