Regulatory Matters - Narrative (Details) GWh in Millions						1 Months Ended		3 Months Ended									6 Months Ended			12 Months Ended
		Dec. 31, 2030	Jun. 30, 2017 USD ($)		Jun. 09, 2017 USD ($)	Jun. 30, 2017 USD ($)		Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)		Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)		Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2017 USD ($) GWh		Jun. 30, 2016 USD ($)	Dec. 31, 2017	Dec. 31, 2016 USD ($)		Jun. 01, 2019	Jun. 01, 2018	Aug. 01, 2017 USD ($)	Jul. 21, 2017 USD ($)	Jun. 01, 2017	Sep. 30, 2016 USD ($)	Aug. 31, 2010 USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Revenues									$ 7,623,000,000					$ 6,910,000,000			$ 16,381,000,000		$ 14,485,000,000
Regulatory Assets			$ 11,238,000,000			$ 11,238,000,000			11,238,000,000			$ 11,388,000,000					11,238,000,000				$ 11,388,000,000
Business Combination, Integration Related Costs	[1],[2]								8,000,000					1,000,000			17,000,000		103,000,000
Capital Expenditures Incurred but Not yet Paid																	105,000,000		364,000,000
Regulatory Liabilities			4,972,000,000			4,972,000,000			4,972,000,000			4,789,000,000					4,972,000,000				4,789,000,000
Regulatory assets			9,945,000,000			9,945,000,000			9,945,000,000			10,046,000,000					9,945,000,000				10,046,000,000
Regulatory Liability, Current			574,000,000			574,000,000			574,000,000			602,000,000					574,000,000				602,000,000
Regulatory Liability, Noncurrent			4,398,000,000			4,398,000,000			4,398,000,000			4,187,000,000					4,398,000,000				4,187,000,000
Liabilities, Current			13,965,000,000			13,965,000,000			13,965,000,000			13,457,000,000					13,965,000,000				13,457,000,000
Other Commitment			3,086,000,000			3,086,000,000			3,086,000,000								3,086,000,000
Fair Value, Net Asset (Liability)			2,400,000,000			2,400,000,000			2,400,000,000								2,400,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
DecouplingImpactOnOperatingRevenuesAndRegulatoryAssets																	$ 36,000,000
CumulativeAnnualEnergyEfficiencyGoal | GWh																	88
Renewable Energy Resources Cumulatively Increase																	1.50%
LowIncomeEnergyAssistanceContributionAnnual																	$ 10,000,000
RenewableEnergyRetailLoad																											50.00%
Revenues									1,357,000,000					1,286,000,000			2,656,000,000		2,535,000,000
Regulatory Assets			1,232,000,000			1,232,000,000			1,232,000,000			1,167,000,000					1,232,000,000				1,167,000,000
Business Combination, Integration Related Costs	[2],[3]								0					1,000,000			1,000,000		(7,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																$ 11,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																	6.47%
Capital Expenditures Incurred but Not yet Paid																	$ 82,000,000		21,000,000
Regulatory Liabilities			3,854,000,000			3,854,000,000			3,854,000,000			3,698,000,000					3,854,000,000				3,698,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount			12,000,000		$ 7,000,000												$ 44,000,000	[4]
Requested Debt and Equity Return on Distribution																	6.47%
Approved ROE	[4],[5]																11.50%
Regulatory assets			1,050,000,000			1,050,000,000			1,050,000,000			977,000,000					$ 1,050,000,000				977,000,000
Public Utilities, Requested Return on Equity, Percentage																	8.40%
Regulatory Liability, Current			269,000,000			269,000,000			269,000,000			329,000,000					$ 269,000,000				329,000,000
Regulatory Liability, Noncurrent			3,585,000,000			3,585,000,000			3,585,000,000			3,369,000,000					3,585,000,000				3,369,000,000
Liabilities, Current			3,750,000,000			3,750,000,000			3,750,000,000			2,938,000,000					3,750,000,000				2,938,000,000
Other Commitment			226,000,000			226,000,000			226,000,000								$ 226,000,000
LowIncomeEnergyAssistanceContributionLength																	5
Low Income Sector Consumption Reduction Targets Act 129 Phase II																	0.10%
SocialCarbonCost																	$ 16.50
NuclearFacilityPurchaseAmount																	$ 0.16
Requested ROE																	8.40%
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount												(18,000,000)					$ 96,000,000				$ 127,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																	6.47%				6.45%
Public Utilities, Requested Rate Increase (Decrease), Amount																	$ 78,000,000				$ 134,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																	$ 18,000,000				$ 7,000,000
Requested Debt and Equity Return on Distribution																	6.47%				6.45%
ICC Approved Rate Increase (Decrease), Amount																	$ 18,000,000				$ 7,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage																	8.40%				8.34%
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
FutureEnergyEfficiencySpending																	$ 250,000,000
Renewable Energy Resources Cumulatively Increase																	11.50%
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
CommercialAndIndustrialCustomerRateIncrease																	1.30%
FutureEnergyEfficiencySpending																	$ 400,000,000
Renewable Energy Resources Cumulatively Increase																	25.00%
ResidentialCustomerRateIncrease																	25.00%
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Total Projected Natural Gas LTIIP Spend									762,000,000							$ 275,000,000
Revenues									630,000,000					664,000,000			$ 1,426,000,000		1,505,000,000
Regulatory Assets			1,778,000,000			1,778,000,000			1,778,000,000			1,710,000,000					1,778,000,000				$ 1,710,000,000
Business Combination, Integration Related Costs	[2]								1,000,000					1,000,000			2,000,000		2,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 22,000,000
Public Utilities, Requested Equity Capital Structure, Percentage									11.00%
Capital Expenditures Incurred but Not yet Paid																	44,000,000		12,000,000
Regulatory Liabilities			699,000,000			699,000,000			$ 699,000,000			644,000,000					699,000,000				644,000,000
Requested Debt and Equity Return on Distribution									11.00%
Regulatory assets			1,732,000,000			1,732,000,000			$ 1,732,000,000			1,681,000,000					1,732,000,000				1,681,000,000
Regulatory Liability, Current			155,000,000			155,000,000			155,000,000			127,000,000					155,000,000				127,000,000
Regulatory Liability, Noncurrent			544,000,000			544,000,000			544,000,000			517,000,000					544,000,000				517,000,000
Liabilities, Current			1,213,000,000			1,213,000,000			1,213,000,000			727,000,000					1,213,000,000				727,000,000
Other Commitment			219,000,000			219,000,000			219,000,000								219,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure	[4],[6]																8,000,000
Revenues									674,000,000					680,000,000			1,625,000,000		1,609,000,000
Regulatory Assets			692,000,000			692,000,000			692,000,000			712,000,000					692,000,000				712,000,000
Business Combination, Integration Related Costs	[2],[7]								1,000,000					(5,000,000)			2,000,000		(4,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																26,000,000
Capital Expenditures Incurred but Not yet Paid																	(6,000,000)		(2,000,000)
Regulatory Liabilities			157,000,000			157,000,000			157,000,000			160,000,000					157,000,000				160,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 31,000,000
Approved ROE	[4],[5]																10.50%
Estimated number of smart meters to be installed																													2,000,000
Total smart grid and smart meter investment grant amount																													$ 480,000,000
Reimbursements received from the DOE																													$ 200,000,000
Regulatory assets			495,000,000			495,000,000			495,000,000			504,000,000					$ 495,000,000				504,000,000
Regulatory Liability, Current			67,000,000			67,000,000			67,000,000			50,000,000					67,000,000				50,000,000
Regulatory Liability, Noncurrent			90,000,000			90,000,000			90,000,000			110,000,000					90,000,000				110,000,000
Liabilities, Current			640,000,000			640,000,000			640,000,000			707,000,000					640,000,000				707,000,000
Other Commitment			263,000,000			263,000,000			263,000,000								263,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues						12,000,000			4,174,000,000					3,589,000,000			9,061,000,000		8,329,000,000
Business Combination, Integration Related Costs	[2]								4,000,000					4,000,000			13,000,000		20,000,000
Unregulated Operating Revenue																	101,000,000
Customer Refund Liability, Noncurrent			20,000,000			20,000,000			20,000,000								20,000,000
Capital Expenditures Incurred but Not yet Paid																	(48,000,000)		317,000,000
Customer Refund			20,000,000			20,000,000			20,000,000								20,000,000
License Costs																	29,000,000
Liabilities, Current			6,064,000,000			6,064,000,000			6,064,000,000			5,683,000,000					6,064,000,000				5,683,000,000
Other Commitment			2,257,000,000			2,257,000,000			2,257,000,000								2,257,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation			3,000,000			3,000,000			3,000,000								3,000,000
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation			7,000,000			7,000,000			7,000,000								7,000,000
PEPCO Holdings Inc [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment			41,000,000			41,000,000			41,000,000								41,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
CapitalProjectFundedByAgency									62,500,000
Revenues									514,000,000					509,000,000			1,045,000,000		1,061,000,000
Regulatory Assets			847,000,000			847,000,000			847,000,000			852,000,000					847,000,000				852,000,000
Business Combination, Integration Related Costs	[2],[8]								1,000,000					$ (4,000,000)			2,000,000		23,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																20,000,000
Capital Expenditures Incurred but Not yet Paid																	0		(11,000,000)
Regulatory Liabilities			22,000,000			22,000,000			22,000,000			31,000,000					22,000,000				31,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 5,000,000
Approved ROE	[4],[5]																10.50%
Regulatory assets			682,000,000			682,000,000			682,000,000			690,000,000					$ 682,000,000				690,000,000
Regulatory Liability, Current			5,000,000			5,000,000			5,000,000			11,000,000					5,000,000				11,000,000
Regulatory Liability, Noncurrent			17,000,000			17,000,000			17,000,000			20,000,000					17,000,000				20,000,000
Liabilities, Current			485,000,000			485,000,000			485,000,000			596,000,000					485,000,000				596,000,000
Other Commitment			20,000,000			20,000,000			20,000,000								20,000,000
Projected Capital Expenditures									500,000,000
Alternative Net Capital Requirement			250,000,000			250,000,000			250,000,000								250,000,000
Capital ProjectFundedByBonds									187,500,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 36,900,000		$ 77,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount											69,000,000								86,000,000
TaxAdjustmentIncludedInPublicUtilitiesRequestedRateIncreaseDecreaseAmount											$ 18,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage									9.50%		10.10%			10.60%
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues									$ 282,000,000					$ 281,000,000			644,000,000		643,000,000
Regulatory Assets			370,000,000			370,000,000			370,000,000			348,000,000					370,000,000				348,000,000
Business Combination, Integration Related Costs	[2],[9]								0					0			(7,000,000)		16,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																14,000,000
Capital Expenditures Incurred but Not yet Paid																	(15,000,000)		9,000,000
Regulatory Liabilities			138,000,000			138,000,000			138,000,000			140,000,000					138,000,000				140,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 6,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount														$ 2,500,000
Approved ROE	[4],[5]																10.50%
Regulatory assets			299,000,000			299,000,000			299,000,000			289,000,000					$ 299,000,000				289,000,000
Public Utilities, Requested Return on Equity, Percentage														10.60%
Regulatory Liability, Current			43,000,000			43,000,000			43,000,000			43,000,000					43,000,000				43,000,000
Regulatory Liability, Noncurrent			95,000,000			95,000,000			95,000,000			97,000,000					95,000,000				97,000,000
Liabilities, Current			417,000,000			417,000,000			417,000,000			381,000,000					417,000,000				381,000,000
Other Commitment			11,000,000			11,000,000			11,000,000								11,000,000
Requested ROE														10.60%
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 4,900,000			10,400,000
Public Utilities, Requested Rate Increase (Decrease), Amount														$ 22,000,000
Public Utilities, Requested Return on Equity, Percentage									9.70%
Gas Revenues Increase Settlement																												$ 0.14
Requested ROE									9.70%
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 31,500,000			29,600,000			$ 32,100,000
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 60,000,000			63,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount											$ 38,000,000
Approved ROE											9.60%
ICC Approved Rate Increase (Decrease), Amount											$ 38,000,000
Public Utilities, Requested Return on Equity, Percentage									9.70%
Projected Capital Expenditures											4,600,000
Requested ROE									9.70%
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure									$ 32,000,000		29,000,000
Revenues									270,000,000					270,000,000			544,000,000		561,000,000
Regulatory Assets			495,000,000			495,000,000			495,000,000			501,000,000					495,000,000				501,000,000
Business Combination, Integration Related Costs	[2]								1,000,000					2,000,000			2,000,000		15,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																42,000,000
Capital Expenditures Incurred but Not yet Paid																	14,000,000		(6,000,000)
Regulatory Liabilities			20,000,000			20,000,000			20,000,000			25,000,000					20,000,000				25,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 20,000,000
Approved ROE	[4],[5]																10.50%
Regulatory assets			406,000,000			406,000,000			406,000,000			405,000,000					$ 406,000,000				405,000,000
Regulatory Liability, Current			20,000,000			20,000,000			20,000,000			25,000,000					20,000,000				25,000,000
Regulatory Liability, Noncurrent			0			0			0			0					0				0
Liabilities, Current			356,000,000			356,000,000			356,000,000			320,000,000					356,000,000				320,000,000
Other Commitment			9,000,000			9,000,000			9,000,000								9,000,000
Projected Capital Expenditures									79,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount									72,600,000		$ 70,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage											10.10%
Renewable Portfolio Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			19,000,000			19,000,000			19,000,000								19,000,000
Renewable Portfolio Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			19,000,000			19,000,000			19,000,000								19,000,000
Recoverable Smart Meter Related Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			32,000,000			32,000,000			32,000,000								32,000,000
MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			3,000,000			3,000,000			3,000,000								3,000,000
MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member] | Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			6,000,000			6,000,000			6,000,000								6,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			4,000,000			4,000,000			4,000,000			4,000,000	[10]				4,000,000				4,000,000	[10]
Advanced Metering Infrastructure Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			29,000,000			29,000,000			29,000,000			23,000,000					29,000,000				23,000,000
Advanced Metering Infrastructure Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			137,000,000			137,000,000			137,000,000								137,000,000
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			69,000,000			69,000,000			69,000,000			89,000,000					69,000,000				89,000,000
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[11]		8,000,000			8,000,000			8,000,000			23,000,000					8,000,000				23,000,000
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			1,000,000			1,000,000			1,000,000			0					1,000,000				0
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[12]		21,000,000			21,000,000			21,000,000			38,000,000					21,000,000				38,000,000
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[13]		6,000,000			6,000,000			6,000,000			6,000,000					6,000,000				6,000,000
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[14]		6,000,000			6,000,000			6,000,000			5,000,000					6,000,000				5,000,000
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[15]		27,000,000	[14]		27,000,000	[14]		27,000,000	[14]		17,000,000					27,000,000	[14]			17,000,000
Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			32,000,000			32,000,000			32,000,000			25,000,000					32,000,000				25,000,000
Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets												0									0
Merger Integration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[16]		7,000,000			7,000,000			7,000,000			10,000,000					7,000,000				10,000,000
Merger Integration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			12,000,000			12,000,000			12,000,000			11,000,000	[10]	9,000,000			12,000,000		9,000,000		11,000,000	[10]
Merger Integration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			13,000,000			13,000,000			13,000,000					3,000,000			13,000,000		3,000,000
Merger Integration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			10,000,000			10,000,000			10,000,000			28,000,000					10,000,000				28,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			4,000,000			4,000,000			4,000,000								4,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			6,000,000			6,000,000			6,000,000			4,000,000					6,000,000				4,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			16,000,000			16,000,000			16,000,000			11,000,000					16,000,000				11,000,000
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			239,000,000			239,000,000			239,000,000			188,000,000					239,000,000				188,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[17]		239,000,000			239,000,000			239,000,000			188,000,000					239,000,000				188,000,000
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			679,000,000			679,000,000			679,000,000			701,000,000					679,000,000				701,000,000
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			163,000,000			163,000,000			163,000,000			164,000,000					163,000,000				164,000,000
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			43,000,000			43,000,000			43,000,000			49,000,000					43,000,000				49,000,000
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			225,000,000			225,000,000			225,000,000			230,000,000					225,000,000				230,000,000
Regulatory assets			225,000,000			225,000,000			225,000,000			230,000,000					225,000,000				230,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets			52,000,000			52,000,000			52,000,000								52,000,000
AMI Expenses [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			167,000,000			167,000,000			167,000,000			174,000,000					167,000,000				174,000,000
AMI Expenses [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			81,000,000			81,000,000			81,000,000			84,000,000					81,000,000				84,000,000
AMI Expenses [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			590,000,000			590,000,000			590,000,000			621,000,000					590,000,000				621,000,000
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Energy Efficiency And Demand Response Programs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			1,000,000			1,000,000			1,000,000			1,000,000					1,000,000				1,000,000
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			271,000,000			271,000,000			271,000,000			285,000,000					271,000,000				285,000,000
Energy Efficiency And Demand Response Programs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			236,000,000			236,000,000			236,000,000			250,000,000					236,000,000				250,000,000
Energy Efficiency And Demand Response Programs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			82,000,000			82,000,000			82,000,000			85,000,000					82,000,000				85,000,000
Energy Efficiency And Demand Response Programs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Legacy AMI [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			56,000,000			56,000,000			56,000,000					$ 56,000,000			56,000,000		$ 56,000,000
Energy Efficiency Program [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			21,000,000			21,000,000			21,000,000								21,000,000
Energy Efficiency Program [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			2,000,000			2,000,000			2,000,000								2,000,000
Zero Emission Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities			22,000,000			22,000,000			22,000,000								22,000,000
Zero Emission Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities			22,000,000			22,000,000			22,000,000								22,000,000
Zero Emission Standard [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues									73,000,000
Renewable Portfolio Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current			10,000,000			10,000,000			10,000,000								10,000,000
Regulatory Liability, Noncurrent			20,000,000			20,000,000			20,000,000								20,000,000
Subsequent Event [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%																		6.60%
RenewableEnergyRetailLoad																							100.00%	75.00%
Purchase Obligation																										$ 170,000,000
Subsequent Event [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																										$ 235,000,000
Subsequent Event [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Customer Refund Liability, Noncurrent																									$ 5,000,000
Customer Refund																									$ 5,000,000
Public Utilities, Requested Return on Equity, Percentage								10.10%
Requested ROE								10.10%
Subsequent Event [Member] | Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount								$ 27,000,000
Pepco Holdings [Member] | Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment			25,600,000			25,600,000			25,600,000								25,600,000
Pepco Holdings [Member] | Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			$ 9,000,000			$ 9,000,000			$ 9,000,000			11,000,000					$ 9,000,000				11,000,000
Business Combination, Integration Related Costs																					8,000,000
Pepco Holdings [Member] | Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[15]											$ 6,000,000									$ 6,000,000

[1] Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.

[2] The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.

[3] For the six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

[4] All rates are effective June 2017, subject to review by the FERC and other parties, which is due by fourth quarter 2017.

[5] As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50% and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55%. As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL and ACE, the rate of return on common equity is 10.50%, inclusive of a 50 basis point incentive adder for being a member of a regional transmission organization.

[6] BGE's transmission revenues include a FERC approved dedicated facilities charge to recover the costs of providing transmission service to specifically designated load by BGE.

[7] (d)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $6 million incurred at BGE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

[8] (e)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

[9] (f)For the six months ended June 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $3 million incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

[10] As of June 30, 2017 and December 31, 2016, Pepco’s regulatory asset of $12 million and $11 million, respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017, DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 million expected to be recovered in electric and gas distribution rates in the Delaware service territory. As of December 31, 2016, DPL's regulatory asset of $4 million represents previously incurred PHI acquisition costs expected to be recovered in distribution rates in the Maryland service territory.

[11] As of June 30, 2017, ComEd’s regulatory asset of $8 million reflects Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2017, ComEd’s regulatory liability of $40 million included $8 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016, ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016, ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements.

[12] As of June 30, 2017, BGE's regulatory asset of $21 million included $10 million related to under-recovered electric energy costs, $5 million related to under-recovered natural gas costs, $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $2 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2016, BGE’s regulatory asset of $38 million included $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $28 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval, and $3 million of under-recovered natural gas costs.

[13] As of June 30, 2017, Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of June 30, 2017, Pepco's regulatory liability of $2 million related to over-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory liability of $8 million included $5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs.

[14] As of June 30, 2017, DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2017, DPL's regulatory liability of $12 million included $10 million of over-recovered electric energy costs and $2 million of over-recovered gas cost. As of December 31, 2016, DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016, DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs.

[15] As of June 30, 2017, ACE's regulatory asset of $27 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $16 million of under-recovered electric energy costs. As of June 30, 2017, ACE's regulatory liability of $8 million related to over-recovered electric energy costs. As of December 31, 2016, ACE's regulatory asset of $17 million included $6 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2016, ACE's regulatory liability of $5 million included $4 million of over-recovered transmission costs and $1 million of over-recovered electric energy costs.

[16] As of June 30, 2017 and December 31, 2016, BGE's regulatory asset of $7 million and $10 million, respectively, included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.

[17] As of June 30, 2017, ComEd’s regulatory asset of $239 million was comprised of $184 million for the 2015 - 2017 annual reconciliations and $55 million related to significant one-time events including $14 million of deferred storm costs, $9 million of Constellation and PHI merger and integration related costs, $3 million of emerald ash borer costs, and $29 million of smart meter related costs. As of December 31, 2016, ComEd’s regulatory asset of $188 million was comprised of $134 million for the 2015 and 2016 annual reconciliations and $54 million related to significant one-time events, including $20 million of deferred storm costs and $11 million of Constellation and PHI merger and integration related costs, and $23 million of smart meter related costs. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information.