Label	Element	Value
Pepco Holdings LLC [Member] | Predecessor [Member]
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	$ 2,000,000
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	0
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	293,000,000
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	(18,000,000)
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(46,000,000)
Proceeds from Contributions from Parent	us-gaap_ProceedsFromContributionsFromParent	0
Payments of Distributions to Affiliates	us-gaap_PaymentsOfDistributionsToAffiliates	0
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	28,000,000
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	0
Cash and Cash Equivalents, at Carrying Value	us-gaap_CashAndCashEquivalentsAtCarryingValue	319,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	11,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	(3,000,000)
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	273,000,000
Gain (Loss) on Disposition of Assets	us-gaap_GainLossOnDispositionOfAssets1	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	0
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	5,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	42,000,000
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	8,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	12,000,000
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	0
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	19,000,000
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	68,000,000
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	372,000,000
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	500,000,000
Payment for Pension and Other Postretirement Benefits	us-gaap_PensionAndOtherPostretirementBenefitContributions	4,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(121,000,000)
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	4,000,000
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	2,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	(3,000,000)
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	1,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(25,000,000)
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	0
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(444,000,000)
Payments of Distributions to Affiliates	us-gaap_PaymentsOfDistributionsToAffiliates	124,000,000
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	(56,000,000)
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	28,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	16,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	34,000,000
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	339,000,000
Gain (Loss) on Disposition of Assets	us-gaap_GainLossOnDispositionOfAssets1	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	39,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	(8,000,000)
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	(35,000,000)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	237,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	22,000,000
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	300,000,000
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	(16,000,000)
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	0
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	137,000,000
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	0
Payment for Pension and Other Postretirement Benefits	us-gaap_PensionAndOtherPostretirementBenefitContributions	2,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	15,000,000
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(537,000,000)
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	0
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	0
Common Stock [Member] | PECO Energy Co [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	0
AOCI Attributable to Parent [Member] | PECO Energy Co [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	$ 0