Significant Accounting Policies (Policy)	6 Months Ended
Significant Accounting Policies (Policy)	Jun. 30, 2011
Significant Accounting Policies
Financial Statement Presentation	Financial Statement Presentation Pepco Holdings' unaudited Consolidated Financial Statements are prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). Pursuant to the rules and regulations of the Securities and Exchange Commission, certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been omitted. Therefore, these financial statements should be read along with the annual financial statements included in PHI's Annual Report on Form 10-K for the year ended December 31, 2010. In the opinion of PHI's management, the Consolidated Financial Statements contain all adjustments (which all are of a normal recurring nature) necessary to present fairly Pepco Holdings' financial condition as of June 30, 2011, in accordance with GAAP. The year-end December 31, 2010 Consolidated Balance Sheet was derived from audited financial statements, but does not include all disclosures required by GAAP. Interim results for the three and six months ended June 30, 2011 may not be indicative of PHI's results that will be realized for the full year ending December 31, 2011, since its Power Delivery business and the retail energy supply business of Pepco Energy Services are seasonal.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosures of contingent assets and liabilities in the Consolidated Financial Statements and accompanying notes. Although Pepco Holdings believes that its estimates and assumptions are reasonable, they are based upon information available to management at the time the estimates are made. Actual results may differ significantly from these estimates. Significant matters that involve the use of estimates include the assessment of goodwill and long-lived assets for impairment, fair value calculations for certain derivative instruments, the costs of providing pension and other postretirement benefits, evaluation of the probability of recovery of regulatory assets, accrual of storm restoration costs, accrual of self-insurance reserves for general and auto liability claims, accrual of interest related to income taxes, accrual of restructuring charges, recognition of changes in network service transmission rates for prior service year costs, and the recognition of income tax benefits for investments in finance leases held in trust associated with PHI's portfolio of cross-border energy lease investments. Additionally, PHI is subject to legal, regulatory, and other proceedings and claims that arise in the ordinary course of its business. PHI records an estimated liability for these proceedings and claims, when it is probable that a loss has been incurred and the loss is reasonably estimable. Network Service Transmission Rates In May 2011, PHI's utility subsidiaries filed their network service transmission rates with the Federal Energy Regulatory Commission to be effective for the service year beginning June 1, 2011. The new rates include an adjustment for costs incurred in the service year ended May 31, 2011 that were not reflected in the rates charged to customers for that service year. In the second quarter of 2011, PHI's utility subsidiaries recorded a $3 million decrease in transmission revenues as a change to the estimates recorded in previous periods primarily due to a decrease in actual rate base versus estimated rate base. General and Auto Liability During the second quarter of 2011, PHI's utility subsidiaries reduced their self-insurance reserves for general and auto liability claims by approximately $4 million, based on obtaining an actuarial estimate of the unpaid loss attributed to general and auto liability claims for each of PHI's utility subsidiaries at June 30, 2011.
Consolidation of Variable Interest Entities	Consolidation of Variable Interest Entities In accordance with the provisions of the Financial Accounting Standards Board (FASB) guidance on the consolidation of variable interest entities (Accounting Standards Codification (ASC) 810), Pepco Holdings consolidates variable interest entities with respect to which Pepco Holdings or a subsidiary is the primary beneficiary. The guidance addresses conditions under which an entity should be consolidated based upon variable interests rather than voting interests. The subsidiaries of Pepco Holdings have contractual arrangements with several entities to which the guidance applies. ACE Power Purchase Agreements PHI, through its ACE subsidiary, is a party to three power purchase agreements (PPAs) with unaffiliated, non-utility generators (NUGs). PHI was unable to obtain sufficient information to determine whether these three entities were variable interest entities or if ACE was the primary beneficiary and as a result has applied the scope exemption from the consolidation guidance for enterprises that have not been able to obtain such information. Net purchase activities with the NUGs for the three months ended June 30, 2011 and 2010, were approximately $55 million and $67 million, respectively, of which approximately $51 million and $62 million, respectively, consisted of power purchases under the PPAs. Net purchase activities with the NUGs for the six months ended June 30, 2011 and 2010, were approximately $112 million and $140 million, respectively, of which approximately $104 million and $129 million, respectively, consisted of power purchases under the PPAs. The power purchase costs are recoverable from ACE's customers through regulated rates. DPL Renewable Energy Transactions PHI, through its DPL subsidiary, has entered into three land-based wind PPAs and one offshore wind PPA in the aggregate amount of 350 megawatts as of June 30, 2011 and one solar PPA with a 10 megawatt facility. As the wind facilities become operational, DPL is obligated to purchase energy and renewable energy credits (RECs) in amounts generated and delivered by the facilities at rates that are primarily fixed under these agreements. Under one of the PPAs, DPL is also obligated to purchase the capacity associated with the facility at rates that are generally fixed. If a wind facility does not become operational by a specified date, DPL has the right to terminate that PPA. One of the land-based facilities is operational and DPL is obligated to purchase energy and RECs from this facility through 2024 in amounts not to exceed 50.25 megawatts. The other two land-based wind agreements each have a 20-year term and are currently expected to become operational during 2011. DPL's purchases under the operational wind PPAs totaled $4 million and $3 million for the three months ended June 30, 2011 and 2010, respectively, and $9 million and $6 million for the six months ended June 30, 2011 and 2010, respectively. In July 2011, the Delaware Public Service Commission (DPSC) approved amendments to one of the land-based wind PPAs to change the location of the facility and to reduce the maximum generation capacity from 60 megawatts to 38 megawatts. The offshore wind PPA is expected to become operational during 2016. If the offshore wind facility developer is unable to obtain all necessary permits and financing commitments, this could result in delays in the construction schedule and the operational start date of the offshore wind facility. The term of the agreement with the solar facility is 20 years and DPL is obligated to purchase RECs in an amount up to 70 percent of the energy output at a fixed price once the facility is operational, which is expected to be in the third quarter of 2011. DPL concluded that consolidation is not required for any of these agreements under FASB guidance on the consolidation of variable interest entities. Atlantic City Electric Transitional Funding LLC Atlantic City Electric Transitional Funding LLC (ACE Funding) was established in 2001 by ACE solely for the purpose of securitizing authorized portions of ACE's recoverable stranded costs through the issuance and sale of bonds (Transition Bonds). The proceeds of the sale of each series of Transition Bonds have been transferred to ACE in exchange for the transfer by ACE to ACE Funding of the right to collect non-bypassable transition bond charges (the Transition Bond Charges) from ACE customers pursuant to bondable stranded costs rate orders issued by the New Jersey Board of Public Utilities (NJBPU) in an amount sufficient to fund the principal and interest payments on the Transition Bonds and related taxes, expenses and fees (Bondable Transition Property). ACE collects the Transition Bond Charges from its customers on behalf of ACE Funding and the holders of the Transition Bonds. The assets of ACE Funding, including the Bondable Transition Property, and the Transition Bond Charges collected from ACE's customers, are not available to creditors of ACE. The holders of the Transition Bonds have recourse only to the assets of ACE Funding. ACE owns 100 percent of the equity of ACE Funding and PHI consolidates ACE Funding in its financial statements as ACE is the primary beneficiary of ACE Funding under the variable interest entity consolidation guidance. ACE Standard Offer Capacity Agreements On April 28, 2011, ACE entered into three Standard Offer Capacity Agreements (SOCAs) by order of the NJBPU, each with a different generation company. The SOCAs were established under a New Jersey law enacted to promote the construction of qualified electric generation facilities in New Jersey. The SOCAs are 15-year, financially settled transactions approved by the NJBPU that allow generators to receive payments from, or make payments to, ACE based on the difference between the fixed price in the SOCAs and the price for capacity that clears PJM Interconnection, LLC (PJM). Each of the other electricity distribution companies (EDCs) in New Jersey has entered into SOCAs having the same terms with the same generation companies. The annual share of payments or receipts for ACE and the other EDCs is based upon each company's annual proportion of the total New Jersey load attributable to all EDCs. ACE and the other EDCs entered the SOCAs under protest based on concerns about the potential cost to distribution customers. On May 16, 2011, the NJBPU denied a joint motion for reconsideration of its order requiring each of the EDCs to enter into the SOCAs. On June 24, 2011, ACE and the other EDCs filed appeals from the NJBPU orders with the Appellate Division of the New Jersey Superior Court. The SOCAs are associated with the construction of three distinct combined cycle, natural gas generation facilities with an aggregate capacity of 1,949 megawatts of which ACE's share would be approximately 15 percent, or 292 megawatts. The obligation to make payments is conditioned upon the clearance of capacity from a generation facility through PJM, and the earliest capacity auction would be in May 2012 based upon the estimated June 1, 2015 operational date for two of the facilities followed by a capacity auction in May 2013 for the third facility that has an estimated June 1, 2016 operational date. Payments would begin after a facility is operational. The NJBPU has approved full recovery from distribution customers of payments made by ACE and the other EDCs, and distribution customers would be entitled to any payments received by ACE and the other EDCs. Currently, PHI believes that FASB guidance on derivative accounting and the accounting for regulated operations would apply to a SOCA once capacity has cleared a PJM auction. Once cleared, the gain (loss) associated with the fair value of a derivative would be offset by the establishment of a regulatory liability (asset). Goodwill Goodwill represents the excess of the purchase price of an acquisition over the fair value of the net assets acquired at the acquisition date. Substantially all of Pepco Holdings' goodwill was generated by Pepco's acquisition of Conectiv in 2002 and is allocated entirely to Pepco Holdings' Power Delivery reporting unit for purposes of impairment testing based on the aggregation of its components. Pepco Holdings tests its goodwill for impairment annually as of November 1 and whenever an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Factors that may result in an interim impairment test include, but are not limited to: a change in the identified reporting units; an adverse change in business conditions; a decline in PHI's stock price causing market capitalization to fall further below book value; an adverse regulatory action; or an impairment of long-lived assets in the reporting unit. PHI concluded that an interim impairment test was not required during the three months ended June 30, 2011 as described in Note (6), "Goodwill." Taxes Assessed by a Governmental Authority on Revenue-Producing Transactions Taxes included in Pepco Holdings' gross revenues were $94 million and $88 million for the three months ended June 30, 2011 and 2010, respectively, and $190 million and $162 million for the six months ended June 30, 2011 and 2010, respectively. Reclassifications and Adjustments Certain prior period amounts have been reclassified in order to conform to the current period presentation. The following adjustments have been recorded and are not considered material either individually or in the aggregate: DPL Default Electricity Supply Revenue and Costs Adjustments During the second quarter of 2011, DPL recorded adjustments to correct certain errors associated with the accounting for Default Electricity Supply revenue and costs. These adjustments primarily arose from the under-recognition of allowed returns on the cost of working capital and resulted in a pre-tax decrease in "Other operation and maintenance" expense of $8 million. Pepco Energy Services Derivative Accounting Adjustments During the first quarter of 2011, PHI recorded an adjustment associated with an increase in the value of certain derivatives from October 1, 2010 to December 31, 2010, which had been erroneously recorded in other comprehensive income at December 31, 2010. This adjustment resulted in an increase in revenue and pre-tax earnings of $2 million. Income Tax Adjustments During the first quarter of 2011, Pepco recorded an adjustment to correct certain income tax errors related to prior periods associated with the interest on uncertain tax positions. The adjustment resulted in an increase in income tax expense of $1 million. During the second quarter of 2010, PHI recorded an adjustment to correct certain income tax errors associated with casualty loss claims, which resulted in a decrease to income tax expense of $1 million for the three and six months ended June 30, 2010. During the first quarter of 2010, ACE recorded an adjustment to correct certain income tax errors related to prior periods. The adjustment resulted in an increase in income tax expense of $6 million for the quarter ended March 31, 2010. The adjustment represents the reversal of erroneously recorded interest income for state income tax purposes related to uncertain and effectively settled tax positions, including $2 million, $3 million and $1 million recorded in 2009, 2008 and 2007, respectively.
Goodwill	Goodwill Goodwill represents the excess of the purchase price of an acquisition over the fair value of the net assets acquired at the acquisition date. Substantially all of Pepco Holdings' goodwill was generated by Pepco's acquisition of Conectiv in 2002 and is allocated entirely to Pepco Holdings' Power Delivery reporting unit for purposes of impairment testing based on the aggregation of its components. Pepco Holdings tests its goodwill for impairment annually as of November 1 and whenever an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Factors that may result in an interim impairment test include, but are not limited to: a change in the identified reporting units; an adverse change in business conditions; a decline in PHI's stock price causing market capitalization to fall further below book value; an adverse regulatory action; or an impairment of long-lived assets in the reporting unit. PHI concluded that an interim impairment test was not required during the three months ended June 30, 2011 as described in Note (6), "Goodwill." Taxes Assessed by a Governmental Authority on Revenue-Producing Transactions Taxes included in Pepco Holdings' gross revenues were $94 million and $88 million for the three months ended June 30, 2011 and 2010, respectively, and $190 million and $162 million for the six months ended June 30, 2011 and 2010, respectively. Reclassifications and Adjustments Certain prior period amounts have been reclassified in order to conform to the current period presentation. The following adjustments have been recorded and are not considered material either individually or in the aggregate: DPL Default Electricity Supply Revenue and Costs Adjustments During the second quarter of 2011, DPL recorded adjustments to correct certain errors associated with the accounting for Default Electricity Supply revenue and costs. These adjustments primarily arose from the under-recognition of allowed returns on the cost of working capital and resulted in a pre-tax decrease in "Other operation and maintenance" expense of $8 million. Pepco Energy Services Derivative Accounting Adjustments During the first quarter of 2011, PHI recorded an adjustment associated with an increase in the value of certain derivatives from October 1, 2010 to December 31, 2010, which had been erroneously recorded in other comprehensive income at December 31, 2010. This adjustment resulted in an increase in revenue and pre-tax earnings of $2 million. Income Tax Adjustments During the first quarter of 2011, Pepco recorded an adjustment to correct certain income tax errors related to prior periods associated with the interest on uncertain tax positions. The adjustment resulted in an increase in income tax expense of $1 million. During the second quarter of 2010, PHI recorded an adjustment to correct certain income tax errors associated with casualty loss claims, which resulted in a decrease to income tax expense of $1 million for the three and six months ended June 30, 2010. During the first quarter of 2010, ACE recorded an adjustment to correct certain income tax errors related to prior periods. The adjustment resulted in an increase in income tax expense of $6 million for the quarter ended March 31, 2010. The adjustment represents the reversal of erroneously recorded interest income for state income tax purposes related to uncertain and effectively settled tax positions, including $2 million, $3 million and $1 million recorded in 2009, 2008 and 2007, respectively.
Taxes Assessed by a Governmental Authority on Revenue-Producing Transactions	Taxes Assessed by a Governmental Authority on Revenue-Producing Transactions Taxes included in Pepco Holdings' gross revenues were $94 million and $88 million for the three months ended June 30, 2011 and 2010, respectively, and $190 million and $162 million for the six months ended June 30, 2011 and 2010, respectively. Reclassifications and Adjustments Certain prior period amounts have been reclassified in order to conform to the current period presentation. The following adjustments have been recorded and are not considered material either individually or in the aggregate: DPL Default Electricity Supply Revenue and Costs Adjustments During the second quarter of 2011, DPL recorded adjustments to correct certain errors associated with the accounting for Default Electricity Supply revenue and costs. These adjustments primarily arose from the under-recognition of allowed returns on the cost of working capital and resulted in a pre-tax decrease in "Other operation and maintenance" expense of $8 million. Pepco Energy Services Derivative Accounting Adjustments During the first quarter of 2011, PHI recorded an adjustment associated with an increase in the value of certain derivatives from October 1, 2010 to December 31, 2010, which had been erroneously recorded in other comprehensive income at December 31, 2010. This adjustment resulted in an increase in revenue and pre-tax earnings of $2 million. Income Tax Adjustments During the first quarter of 2011, Pepco recorded an adjustment to correct certain income tax errors related to prior periods associated with the interest on uncertain tax positions. The adjustment resulted in an increase in income tax expense of $1 million. During the second quarter of 2010, PHI recorded an adjustment to correct certain income tax errors associated with casualty loss claims, which resulted in a decrease to income tax expense of $1 million for the three and six months ended June 30, 2010. During the first quarter of 2010, ACE recorded an adjustment to correct certain income tax errors related to prior periods. The adjustment resulted in an increase in income tax expense of $6 million for the quarter ended March 31, 2010. The adjustment represents the reversal of erroneously recorded interest income for state income tax purposes related to uncertain and effectively settled tax positions, including $2 million, $3 million and $1 million recorded in 2009, 2008 and 2007, respectively.
Reclassifications and Adjustments	Reclassifications and Adjustments Certain prior period amounts have been reclassified in order to conform to the current period presentation. The following adjustments have been recorded and are not considered material either individually or in the aggregate: DPL Default Electricity Supply Revenue and Costs Adjustments During the second quarter of 2011, DPL recorded adjustments to correct certain errors associated with the accounting for Default Electricity Supply revenue and costs. These adjustments primarily arose from the under-recognition of allowed returns on the cost of working capital and resulted in a pre-tax decrease in "Other operation and maintenance" expense of $8 million. Pepco Energy Services Derivative Accounting Adjustments During the first quarter of 2011, PHI recorded an adjustment associated with an increase in the value of certain derivatives from October 1, 2010 to December 31, 2010, which had been erroneously recorded in other comprehensive income at December 31, 2010. This adjustment resulted in an increase in revenue and pre-tax earnings of $2 million. Income Tax Adjustments During the first quarter of 2011, Pepco recorded an adjustment to correct certain income tax errors related to prior periods associated with the interest on uncertain tax positions. The adjustment resulted in an increase in income tax expense of $1 million. During the second quarter of 2010, PHI recorded an adjustment to correct certain income tax errors associated with casualty loss claims, which resulted in a decrease to income tax expense of $1 million for the three and six months ended June 30, 2010. During the first quarter of 2010, ACE recorded an adjustment to correct certain income tax errors related to prior periods. The adjustment resulted in an increase in income tax expense of $6 million for the quarter ended March 31, 2010. The adjustment represents the reversal of erroneously recorded interest income for state income tax purposes related to uncertain and effectively settled tax positions, including $2 million, $3 million and $1 million recorded in 2009, 2008 and 2007, respectively.

Describe any adjustments made during the period to avoid double counting in comprehensive income items displayed as part of net income that also had been displayed as part of other comprehensive income in that period or earlier periods. These adjustments include reclassifications to net income of items in accumulated comprehensive income, such as deferred gains (losses) on qualifying hedges when hedged item reported in net income, holding gains (losses) on available-for-sale securities transferred into trading category, unrealized holding gains (losses) on debt securities transferred from held-to-maturity category into available-for-sale category and accumulated translation adjustment attributable to foreign subsidiary or investment in foreign entity upon sale or liquidation.

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