Label	Element	Value
Successor [Member]
Impairment of Long-Lived Assets Held-for-use	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse	$ 0
Predecessor [Member]
Impairment of Long-Lived Assets Held-for-use	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse	0
PECO Energy Co [Member] | Over-Recovered Electric Transmission Cost [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	3,000,000
PECO Energy Co [Member] | DSP Program costs [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	35,000,000
PECO Energy Co [Member] | OverRecoveredNaturalGasSupply [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	$ 22,000,000
PECO Energy Co [Member] | Minimum [Member] | Energy Efficiency And Demand Response Programs [Member]
Cumulative Consumption Reduction Targets	exc_CumulativeConsumptionReductionTargets	1,962,659
Pepco Holdings LLC [Member] | Successor [Member]
Increase (Decrease) Cash Collateral from Counterparties	us-gaap_IncreaseDecreaseCashCollateralFromCounterparties	$ 0
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(1,030,000,000)
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	37,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	338,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(149,000,000)
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	(7,000,000)
Proceeds from Stock Plans	us-gaap_ProceedsFromStockPlans	0
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	(5,000,000)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	311,000,000
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	0
Proceeds from (Repayments of) Short-term Debt	us-gaap_ProceedsFromRepaymentsOfShortTermDebt	(515,000,000)
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	42,000,000
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	300,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	24,000,000
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(514,000,000)
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	295,000,000
Increase (Decrease) in Due to Affiliates	us-gaap_IncreaseDecreaseInDueToAffiliates	(6,000,000)
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	0
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	21,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	19,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	9,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax	0
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	(3,000,000)
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	179,000,000
Net Cash Provided by (Used in) Operating Activities	us-gaap_NetCashProvidedByUsedInOperatingActivities	888,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	(22,000,000)
Proceeds from Issuance of Preferred Stock and Preference Stock	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0
Pepco Holdings LLC [Member] | Predecessor [Member]
Increase (Decrease) Cash Collateral from Counterparties	us-gaap_IncreaseDecreaseCashCollateralFromCounterparties	1,000,000
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(343,000,000)
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	(3,000,000)
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	11,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	293,000,000
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	372,000,000
Proceeds from Stock Plans	us-gaap_ProceedsFromStockPlans	2,000,000
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	2,000,000
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	9,000,000
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	500,000,000
Proceeds from (Repayments of) Short-term Debt	us-gaap_ProceedsFromRepaymentsOfShortTermDebt	(121,000,000)
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	68,000,000
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	0
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	0
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	0
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(46,000,000)
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	19,000,000
Increase (Decrease) in Due to Affiliates	us-gaap_IncreaseDecreaseInDueToAffiliates	0
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	(18,000,000)
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	28,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	42,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	5,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax	0
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	4,000,000
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	0
Net Cash Provided by (Used in) Operating Activities	us-gaap_NetCashProvidedByUsedInOperatingActivities	264,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	12,000,000
Proceeds from Issuance of Preferred Stock and Preference Stock	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0
Baltimore Gas and Electric Company [Member] | Stride Program [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	2,000,000
Captial and OM estimates current year	exc_CapitalandOMestimatescurrentyear	131,000,000
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	10,358,000,000
Retained Earnings [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Members' Equity	us-gaap_MembersEquity	0
Retained Earnings [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1,005,000,000
Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	(2,327,000,000)
Common Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	16,741,000,000
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions	(18,000,000)
Common Stock [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1,360,000,000
AOCI Attributable to Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	(2,040,000,000)
AOCI Attributable to Parent [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Members' Equity	us-gaap_MembersEquity	0
AOCI Attributable to Parent [Member] | Exelon Generation Co L L C [Member]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	(54,000,000)
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	15,000,000
Noncontrolling Interest [Member] | Exelon Generation Co L L C [Member]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	us-gaap_NoncontrollingInterestIncreaseFromSaleOfParentEquityInterest	2,000,000
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	1,774,000,000
Common Stock Including Additional Paid in Capital [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Members' Equity	us-gaap_MembersEquity	7,200,000,000	[1]
Business Combination, Contingent Consideration, Liability, Noncurrent	us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent	53,000,000
Preference Stock Not Subject To Mandatory Redemption [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	193,000,000
Preference Stock Not Subject To Mandatory Redemption [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	190,000,000
Undistributed Earnings [Member] | Exelon Generation Co L L C [Member]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	2,275,000,000
Membership Interest [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2,365,000,000
Membership Interest [Member] | Exelon Generation Co L L C [Member]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	9,261,000,000
Pepco Holdings LLC [Member] | Commitments [Member] | Successor [Member]
Payments to Acquire Businesses, Gross	us-gaap_PaymentsToAcquireBusinessesGross	$ 33,000,000

[1] The March 24, 2016, beginning balance differs from the PHI Merger total purchase price by $59 million related to an acquisition accounting adjustment recorded at Exelon Corporate to reflect unitary state income tax consequences of the merger.