Debt (Components Of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified									3 Months Ended	12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended					12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended								12 Months Ended		12 Months Ended				12 Months Ended						12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Pepco Energy Services [Member]	Dec. 31, 2010 Pepco Energy Services [Member]	Dec. 31, 2011 First Mortgage Bonds [Member]		Dec. 31, 2010 First Mortgage Bonds [Member]		Jun. 30, 2011 First Mortgage Bonds [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 4.95% Due 2013 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 4.95% Due 2013 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 4.65% Due 2014 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 4.65% Due 2014 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 6.20% Due 2022 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 6.20% Due 2022 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 5.375% Due 2024 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 5.375% Due 2024 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 5.75% Due 2034 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 5.75% Due 2034 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 5.40% Due 2035 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 5.40% Due 2035 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 7.90% Due 2038 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 7.90% Due 2038 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 6.50% Due 2037 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 6.50% Due 2037 [Member] Potomac Electric Power Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 7.63% Due 2014 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 7.63% Due 2014 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 6.63% Due 2013 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 6.63% Due 2013 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 7.68% Due 2015 - 2016 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 7.68% Due 2015 - 2016 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 7.75% Due 2018 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 7.75% Due 2018 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 6.80% Due 2021 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 6.80% Due 2021 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 4.35% Due 2021 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 5.60% Due 2025 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 5.60% Due 2025 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 4.875% Due 2029 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 4.875% Due 2029 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 5.80% Due 2034 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 5.80% Due 2034 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 5.80% Due 2036 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 5.80% Due 2036 [Member] Atlantic City Electric Co [Member]		Dec. 31, 2011 First Mortgage Bonds [Member] 6.40% Due 2013 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 6.40% Due 2013 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 5.22% Due 2016 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 5.22% Due 2016 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 5.20% Due 2019 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 First Mortgage Bonds [Member] 5.20% Due 2019 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 First Mortgage Bonds [Member] 0.75% - 4.90% Due 2026 [Member] Delmarva Power & Light Co/De [Member]		Dec. 31, 2010 First Mortgage Bonds [Member] 0.75% - 4.90% Due 2026 [Member] Delmarva Power & Light Co/De [Member]		Dec. 31, 2011 Unsecured Tax-Exempt Bonds [Member]		Dec. 31, 2010 Unsecured Tax-Exempt Bonds [Member]		Dec. 31, 2011 Unsecured Tax-Exempt Bonds [Member] 1.80% Due 2025 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Unsecured Tax-Exempt Bonds [Member] 1.80% Due 2025 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Unsecured Tax-Exempt Bonds [Member] 2.30% Due 2028 [Member] Delmarva Power & Light Co/De [Member]		Dec. 31, 2010 Unsecured Tax-Exempt Bonds [Member] 2.30% Due 2028 [Member] Delmarva Power & Light Co/De [Member]		Dec. 31, 2011 Unsecured Tax-Exempt Bonds [Member] 5.40% Due 2031 [Member] Delmarva Power & Light Co/De [Member]		Dec. 31, 2010 Unsecured Tax-Exempt Bonds [Member] 5.40% Due 2031 [Member] Delmarva Power & Light Co/De [Member]		Dec. 31, 2011 Medium-Term Notes [Member]	Dec. 31, 2010 Medium-Term Notes [Member]	Dec. 31, 2011 Medium-Term Notes [Member] 7.56% - 7.58% Due 2017 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Medium-Term Notes [Member] 7.56% - 7.58% Due 2017 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Medium-Term Notes [Member] 6.81% Due 2018 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Medium-Term Notes [Member] 6.81% Due 2018 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Medium-Term Notes [Member] 7.61% Due 2019 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Medium-Term Notes [Member] 7.61% Due 2019 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Medium-Term Notes [Member] 7.72% Due 2027 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Medium-Term Notes [Member] 7.72% Due 2027 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Recourse Debt [Member] 6.59% - 6.69% Due 2014 [Member]	Dec. 31, 2010 Recourse Debt [Member] 6.59% - 6.69% Due 2014 [Member]	Dec. 31, 2011 Secured Notes [Member] 7.35% - 7.47% Due 2017 [Member] Pepco Energy Services [Member]	Dec. 31, 2010 Secured Notes [Member] 7.35% - 7.47% Due 2017 [Member] Pepco Energy Services [Member]	Dec. 31, 2011 Unsecured Notes [Member]	Dec. 31, 2010 Unsecured Notes [Member]	Dec. 31, 2011 Unsecured Notes [Member] 2.70% Due 2015 [Member]	Dec. 31, 2010 Unsecured Notes [Member] 2.70% Due 2015 [Member]	Dec. 31, 2011 Unsecured Notes [Member] 5.90% Due 2016 [Member]	Dec. 31, 2010 Unsecured Notes [Member] 5.90% Due 2016 [Member]	Dec. 31, 2011 Unsecured Notes [Member] 6.125% Due 2017 [Member]	Dec. 31, 2010 Unsecured Notes [Member] 6.125% Due 2017 [Member]	Dec. 31, 2011 Unsecured Notes [Member] 7.45% Due 2032 [Member]	Dec. 31, 2010 Unsecured Notes [Member] 7.45% Due 2032 [Member]	Dec. 31, 2011 Unsecured Notes [Member] 5.00% Due 2014 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Unsecured Notes [Member] 5.00% Due 2014 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Unsecured Notes [Member] 5.00% Due 2015 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2010 Unsecured Notes [Member] 5.00% Due 2015 [Member] Delmarva Power & Light Co/De [Member]	Dec. 31, 2011 Transition Bonds [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 Transition Bonds [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 Transition Bonds [Member] 4.21% Due 2013 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 Transition Bonds [Member] 4.21% Due 2013 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 Transition Bonds [Member] 4.46% Due 2016 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 Transition Bonds [Member] 4.46% Due 2016 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 Transition Bonds [Member] 4.91% Due 2017 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 Transition Bonds [Member] 4.91% Due 2017 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 Transition Bonds [Member] 5.05% Due 2020 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 Transition Bonds [Member] 5.05% Due 2020 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2011 Transition Bonds [Member] 5.55% Due 2023 [Member] Atlantic City Electric Co [Member]	Dec. 31, 2010 Transition Bonds [Member] 5.55% Due 2023 [Member] Atlantic City Electric Co [Member]
Debt Instrument [Line Items]
Debt instrument, carrying value					$ 2,798	[1],[2]	$ 2,598	[1],[2]		$ 200	[1]	$ 200	[1]	$ 175	[1],[3]	$ 175	[1],[3]	$ 110	[1],[3]	$ 110	[1],[3]	$ 38	[1],[3],[4]	$ 38	[1],[3],[4]	$ 100	[1]	$ 100	[1]	$ 175	[1],[3]	$ 175	[1],[3]	$ 250	[1],[3],[4]	$ 250	[1],[3],[4]	$ 500	[1],[3]	$ 500	[1],[3]	$ 7	$ 7	$ 69	$ 69	$ 17	$ 17	$ 250	$ 250	$ 39	$ 39	$ 200	$ 4	[1]	$ 4	[1]	$ 23	[1]	$ 23	[1]	$ 120	[1],[3],[4]	$ 120	[1],[3],[4]	$ 105	[1],[3]	$ 105	[1],[3]	$ 250	$ 250	$ 100	$ 100	$ 31	$ 31	$ 35	[1]	$ 35	[1]	$ 109	[5]	$ 109	[5]	$ 15	$ 15	$ 16	[6]	$ 16	[6]	$ 78	[5]	$ 78	[5]	$ 40	$ 40	$ 14	$ 14	$ 4	$ 4	$ 12	$ 12	$ 10	$ 10	$ 11	$ 11	$ 15	$ 11	$ 906	$ 906	$ 250	$ 250	$ 190	$ 190	$ 81	$ 81	$ 185	$ 185	$ 100	$ 100	$ 100	$ 100				$ 9	$ 29	$ 39	$ 102	$ 118	$ 54	$ 54	$ 147	$ 147
Debt interest percentage									4.35%	4.95%				4.65%				6.20%				5.375%				5.75%				5.40%				7.90%				6.50%				7.63%		6.63%		7.68%		7.75%		6.80%		4.35%	5.60%				4.875%				5.80%				5.80%				6.40%		5.22%		5.20%										1.80%		2.30%				5.40%								6.81%		7.61%		7.72%								2.70%		5.90%		6.125%		7.45%		5.00%		5.00%				4.21%		4.46%		4.91%		5.05%		5.55%
Debt instrument percentage, minimum																																																																											0.75%																				7.56%								6.59%		7.35%
Debt instrument percentage, maximum																																																																											4.90%																				7.58%								6.69%		7.47%
Debt instrument percentage, previously stated																																																																																			5.50		5.65
Debt instrument maturity date									April 1, 2021	2013	[1]			2014	[1],[3]			2022	[1],[3]			2024	[1],[3],[4]			2034	[1]			2035	[1],[3]			2038	[1],[3],[4]			2037	[1],[3]			2014		2013				2018		2021		2021	2025	[1]			2029	[1]			2034	[1],[3],[4]			2036	[1],[3]			2013		2016		2019		2026	[1]							2025		2028	[6]			2031	[5]					2017		2018		2019		2027		2014		2017				2015		2016		2017		2032		2014		2015				2013		2016		2017		2020		2023
Debt instrument maturity date, start																																														2015
Debt instrument maturity date, end																																														2016
Total Long-Term Debt	3,879	3,675							200																																																																																																																332	367
Other long-term debt		2	15	19
Net unamortized discount	(12)	(12)
Current portion of long-term debt	(73)	(36)																																																																																																																							(37)	(35)
Total Net Long-Term Debt	$ 3,794	$ 3,629																																																																																																																							$ 295	$ 332

[1] Represents a series of first mortgage bonds issued by the indicated company (Collateral First Mortgage Bonds) as collateral for an outstanding series of senior notes issued by the company or tax-exempt bonds issued for the benefit of the company. The maturity date, optional and mandatory prepayment provisions, if any, interest rate, and interest payment dates on each series of senior notes or the company's obligations in respect of the tax-exempt bonds are identical to the terms of the corresponding series of Collateral First Mortgage Bonds. Payments of principal and interest on a series of senior notes or the company's obligations in respect of the tax-exempt bonds satisfy the corresponding payment obligations on the related series of Collateral First Mortgage Bonds. Because each series of senior notes or the company's obligations in respect of the tax-exempt bonds and the corresponding series of Collateral First Mortgage Bonds securing that series of senior notes or tax-exempt bonds obligations effectively represents a single financial obligation, the senior notes and the tax-exempt bonds are not separately shown on the table.

[2] These bonds bearing an interest rate of 4.90% were repurchased. On June 1, 2011, DPL resold these bonds that were subject to mandatory repurchase on May 1, 2011 at an interest rate of 0.75%. The bonds are currently subject to mandatory tender on June 1, 2012.

[3] Represents a series of Collateral First Mortgage Bonds issued by the indicated company that in accordance with its terms will, at such time as there are no first mortgage bonds of the issuing company outstanding (other than Collateral First Mortgage Bonds securing payment of senior notes), cease to secure the corresponding series of senior notes and will be cancelled.

[4] Represents a series of Collateral First Mortgage Bonds as to which the indicated company has agreed in connection with the issuance of the corresponding series of senior notes that, notwithstanding the terms of the Collateral First Mortgage Bonds described in footnote (b) above, it will not permit the release of the Collateral First Mortgage Bonds as security for the series of senior notes for so long as the senior notes remain outstanding, unless the company delivers to the senior note trustee comparable secured obligations to secure the senior notes.

[5] On July 1, 2010, DPL purchased this series of tax-exempt bonds issued for the benefit of DPL by the Delaware Economic Development Authority (DEDA) pursuant to a mandatory repurchase provision in the indenture for the bonds that was triggered by the expiration of the original interest period for the bonds. While DPL held the bonds, they remained outstanding as a contractual matter, but were considered extinguished for accounting purposes. On December 1, 2010, DPL resold the bonds to the public, at which time the interest rate on the bonds was changed from 5.50% to a fixed rate of 1.80%. The bonds are subject to mandatory purchase by DPL on June 1, 2012.

[6] On July 1, 2010, DPL purchased this series of tax-exempt bonds issued for the benefit of DPL by DEDA pursuant to a mandatory repurchase provision in the indenture for the bonds that was triggered by the expiration of the original interest period for the bonds. While DPL held the bonds, they remained outstanding as a contractual matter, but were considered extinguished for accounting purposes. On December 1, 2010, DPL resold the bonds to the public, at which time the interest rate on the bonds was changed from 5.65% to a fixed rate of 2.30%. The bonds are subject to mandatory purchase by DPL on June 1, 2012.