Label	Element	Value
Pepco Holdings LLC [Member] | Predecessor [Member]
Payments of Ordinary Dividends, Common Stock	us-gaap_PaymentsOfDividendsCommonStock	$ 0
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	293,000,000
Proceeds from Issuance of Preferred Stock and Preference Stock	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	5,000,000
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	2,000,000
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	2,000,000
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	0
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	0
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	12,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	42,000,000
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(46,000,000)
Increase Decrease In Counterparty Collateral Net	exc_IncreaseDecreaseInCounterpartyCollateralNet	(1,000,000)
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	11,000,000
Pension and Other Postretirement Benefit Contributions	us-gaap_PensionAndOtherPostretirementBenefitContributions	4,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	(3,000,000)
Distribution to members	exc_DistributionToMembers	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	0
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	(18,000,000)
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(343,000,000)
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(121,000,000)
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	500,000,000
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	28,000,000
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	19,000,000
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	4,000,000
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	68,000,000
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	273,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Payments of Ordinary Dividends, Common Stock	us-gaap_PaymentsOfDividendsCommonStock	0
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(25,000,000)
Proceeds from Issuance of Preferred Stock and Preference Stock	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	(8,000,000)
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	0
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
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	28,000,000
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
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	(35,000,000)
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(444,000,000)
Increase Decrease In Counterparty Collateral Net	exc_IncreaseDecreaseInCounterpartyCollateralNet	0
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	16,000,000
Pension and Other Postretirement Benefit Contributions	us-gaap_PensionAndOtherPostretirementBenefitContributions	2,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	34,000,000
Distribution to members	exc_DistributionToMembers	(124,000,000)
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	39,000,000
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	0
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(350,000,000)
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(537,000,000)
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	0
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	(56,000,000)
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	(16,000,000)
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	0
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	15,000,000
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	0
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	$ 339,000,000