Regulatory Matters - Narrative (Details) GWh in Millions																		1 Months Ended		3 Months Ended										6 Months Ended	9 Months Ended	12 Months Ended						60 Months Ended	65 Months Ended
		Dec. 31, 2030	Jan. 02, 2018 GWh	Jul. 29, 2016 USD ($)	Nov. 30, 2015 MWh	Nov. 06, 2015 USD ($)	Sep. 10, 2015 USD ($)	May 27, 2015 USD ($)	May 07, 2015 USD ($)	Mar. 27, 2015 USD ($)	Sep. 15, 2014 USD ($)	Aug. 21, 2014 USD ($)	Mar. 15, 2013 USD ($)	Dec. 05, 2012	Nov. 01, 2012 MWh	Jul. 31, 2012 USD ($)	Apr. 30, 2012 MW	Mar. 31, 2013 USD ($)	Aug. 31, 2010 USD ($) smart_meter	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) smart_meter	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 23, 2016 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2008 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) smart_meter	Dec. 31, 2017	Dec. 31, 2016 USD ($) smart_meter	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013	Dec. 31, 2007 USD ($)	Nov. 30, 2010 USD ($)	Nov. 30, 2005 USD ($)	Jun. 01, 2019	Jun. 01, 2018	Jun. 01, 2017	Jun. 03, 2016 USD ($)	Mar. 31, 2015 USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent																					$ 14,000,000										$ 14,000,000		$ 14,000,000	$ 90,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount																																	138	(50)	$ 269
Regulatory Assets																					11,388,000,000										11,388,000,000		11,388,000,000	6,824,000,000
Noncurrent regulatory assets																					10,046,000,000										10,046,000,000		10,046,000,000	6,065,000,000
Regulatory liabilities																					602,000,000										602,000,000		602,000,000	369,000,000
Business Combination, Integration Related Costs	[1],[2]																																143,000,000	87,000,000
Regulatory Liabilities																					4,789,000,000										4,789,000,000		4,789,000,000	4,570,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	128,000,000	96,000,000	220,000,000
Other Commitment																					513,000,000		$ 137,000,000							$ 137,000,000	513,000,000		513,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					72,000,000										72,000,000		72,000,000	55,000,000
Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					185,000,000										185,000,000		185,000,000	92,000,000
Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					134,000,000										134,000,000		$ 134,000,000	131,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Subsequent contribution to technology innovation trust																$ 4,000,000
Utility annual customer assistance																$ 10,000,000
Term of contract																																	20 years
Low income sector consumption reduction targets Act 129 Phase II																																	0.10%
Renewable energy resources cumulatively increase																																	1.50%
Public Utilities, Requested Rate Increase (Decrease), Amount																																	$ 90,000,000	68,000,000	36,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	(4,000,000)	(18,000,000)	14,000,000
Regulatory Assets																					1,167,000,000										1,167,000,000		1,167,000,000	1,113,000,000
Noncurrent regulatory assets																					977,000,000										977,000,000		$ 977,000,000	895,000,000
Rate of return on common equity in federal energy regulatory committee complaint																																	11.50%
Regulatory liabilities																					329,000,000										329,000,000		$ 329,000,000	155,000,000
Business Combination, Integration Related Costs	[2],[3]																																(6,000,000)	9,000,000
Regulatory Liabilities																					3,698,000,000										3,698,000,000		3,698,000,000	3,614,000,000
Customer refundable fees, interest																																		1,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	(94,000,000)	(86,000,000)	(22,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 91,000,000	$ 34,000,000	$ 78,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																																	8.47%	8.61%	8.62%
Public Utilities, Requested Return on Equity, Percentage																																		11.50%	11.50%
Public Utilities, Interim Rate Increase (Decrease), Amount																																	$ (8,000,000)
SocialCarbonCost																																	16.50
NuclearFacilityPurchaseAmount																																	0.16
LowIncomeEnergyAssistanceContributionAnnual																																	$ 10,000,000
LowIncomeEnergyAssistanceContributionLength																																	5
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					5,000,000										5,000,000		$ 5,000,000	$ 6,000,000
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					141,000,000										141,000,000		141,000,000	52,000,000
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					60,000,000										60,000,000		60,000,000	53,000,000
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					30,000,000										30,000,000		30,000,000	24,000,000
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					30,000,000										$ 30,000,000		30,000,000	29,000,000
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	134	85	$ 160
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																					$ 18,000,000												$ (127)	$ 67	$ (232)
Public Utilities, Approved Return on Equity, Percentage																																	8.59%	9.09%	9.20%
Public Utilities, Approved Rate Increase (Decrease), Amount																																	$ 7	$ 152	$ (72)
Public Utilities, Requested Equity Capital Structure, Percentage																																	6.71%	7.05%	7.06%
Public Utilities, Requested Return on Equity, Percentage																																	8.64%	9.14%	9.25%
Commonwealth Edison Co [Member] | Energy Related Derivative [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Term of contract																																	20 years
Commonwealth Edison Co [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%																														6.60%
RenewableEnergyRetailLoad																																								100.00%	100.00%	100.00%
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Renewable energy resources cumulatively increase																																	11.50%
FutureEnergyEfficiencySpending																																	$ 250,000,000
EnergyEfficiencyROEAdjustment																																	20000.00%
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Renewable energy resources cumulatively increase																																	25.00%
FutureEnergyEfficiencySpending																																	$ 400,000,000
ResidentialCustomerRateIncrease																																	25.00%
CommercialAndIndustrialCustomerRateIncrease																																	1.30%
Commonwealth Edison Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
CumulativeAnnualEnergyEfficiencyGoal | GWh			88
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Low income sector consumption reduction targets Act 129 Phase II														4.50%
Smart meters initial phase deployment | smart_meter																					1,600,000.0										1,600,000.0		1,600,000.0
Estimated number of smart meters to be installed | smart_meter																					1,700,000										1,700,000		1,700,000
Total smart grid smart meter investment grant awarded																					$ 200,000,000										$ 200,000,000		$ 200,000,000
Total smart meter spend on investment																					578,000,000										578,000,000		578,000,000
Total smart grid spend on investment																					155,000,000										155,000,000		155,000,000
Smart grid investment grant awarded								$ 275,000,000	$ 534,000,000
Cumulative consumption reduction targets | MWh															1,125,852
Public sector maximum consumption reduction targets Act 129 Phase II														10.00%
Proposed funding Of direct load control program costs													$ 10,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 127,000,000			$ 190,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										10.95%
Regulatory Assets																					1,710,000,000										1,710,000,000		1,710,000,000	$ 1,617,000,000
Noncurrent regulatory assets																					1,681,000,000										1,681,000,000		1,681,000,000	1,583,000,000
Regulatory liabilities																					127,000,000										127,000,000		127,000,000	112,000,000
Business Combination, Integration Related Costs	[2]																																5,000,000	4,000,000
Regulatory Liabilities																					644,000,000										644,000,000		644,000,000	639,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	11,000,000	13,000,000	$ 0
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					0										0		0	0
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					10,000,000										10,000,000		10,000,000
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					41,000,000										41,000,000		41,000,000	40,000,000
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					56,000,000										56,000,000		56,000,000	60,000,000
PECO Energy Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Percentage Tier I alternative energy resources																																				3.50%
Percentage Tier II alternative energy resources																																				6.20%
PECO Energy Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Low income sector consumption reduction targets Act 129 Phase II														2.00%
Cumulative consumption reduction targets | MWh					2,100,875
Percentage Tier I alternative energy resources																																				8.00%
Percentage Tier II alternative energy resources																																				10.00%
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase in electric delivery service revenue resulting from rate case settlement or order.																																		22,000,000
Increase in gas delivery service revenue resulting from rate case settlement or order.																																		38,000,000
Estimated number of smart meters to be installed | smart_meter																			2,000,000
Projected investment in smart meters						$ 104,000,000															37,000,000										37,000,000		37,000,000
Annual depreciation expense decrease regulated property												$ 20,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount																																	12,000,000	0	9,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount											$ (68,000,000)															$ (99,000,000)							(3,000,000)	3,000,000	(5,000,000)
Regulatory Assets																					712,000,000										712,000,000		712,000,000	781,000,000
Total projected smart meter smart grid spend																			$ 480,000,000
Reimbursements received from the DOE																			$ 200,000,000
Noncurrent regulatory assets																					504,000,000										504,000,000		504,000,000	514,000,000
Customer Refund Liability, Noncurrent																																											$ 30,000,000
Regulatory liabilities																					50,000,000										50,000,000		50,000,000	38,000,000
Business Combination, Integration Related Costs	[2],[3]																																(1,000,000)	5,000,000
Site contingency, recovery from third party of environmental remediation cost																																						$ 1,000,000	$ 5,000,000
Regulatory Liabilities																					160,000,000										160,000,000		$ 160,000,000	222,000,000
Deferred costs, noncurrent																		$ 16,000,000																										$ 8,000,000
Rate cap imposed on public utility subsidiary																																	15.00%
Deferred purchased power costs																																					$ 306,000,000
Environmental costs recognized, recovery credited to expense																																	$ 81,000,000	73,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	(28,000,000)	(10,000,000)	(17,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 86,000,000	$ 9,000,000	$ 25,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																																	8.09%	8.46%	8.53%
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					57,000,000										57,000,000		$ 57,000,000	$ 49,000,000
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		1,000,000
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					0										0		0	0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					9,000,000										9,000,000		9,000,000	19,000,000
Regulatory Liabilities																					0										0		0	18,000,000
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					2,000,000										2,000,000		2,000,000
Baltimore Gas and Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		14,000,000
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		5,000,000
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Gas Revenue [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		1,000,000
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Electric Revenue [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		30,000,000
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	116,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount				$ (44,000,000)
Public Utilities, Requested Return on Equity, Percentage						9.80%
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	78,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount				$ (48,000,000)
Public Utilities, Requested Return on Equity, Percentage						9.70%
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent																					14,000,000										14,000,000		14,000,000	90,000,000
Customer Refund Liability, Noncurrent																					20,000,000										20,000,000		20,000,000
Business Combination, Integration Related Costs	[2]																																37,000,000	24,000,000
Unregulated Operating Revenue																																	101,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	50,000,000	82,000,000	$ 61,000,000
Exelon Generation Co L L C [Member] | Conowingo [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License costs																																	28,000,000
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Business Combination, Integration Related Costs	[2],[3]																																28,000,000	3,000,000
Other Commitment																								$ 444,000,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		2,582,000,000
Noncurrent regulatory assets																																		2,277,000,000
Regulatory liabilities																																		66,000,000
Business Combination, Integration Related Costs	[3]																								$ 29,000,000								19,000,000
Regulatory Liabilities																																		213,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																									$ 11,000,000									6,000,000	28,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																																		4,000,000
Pepco Holdings LLC [Member] | Predecessor [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		1,000,000
Pepco Holdings LLC [Member] | Predecessor [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		27,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					3,504,000,000										3,504,000,000		3,504,000,000
Noncurrent regulatory assets																					2,851,000,000										2,851,000,000		2,851,000,000
Regulatory liabilities																					79,000,000										79,000,000		79,000,000
Business Combination, Integration Related Costs	[3]																														69,000,000
Regulatory Liabilities																					237,000,000										237,000,000		237,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																															21,000,000
Other Commitment																					323,000,000										323,000,000		323,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					10,000,000										10,000,000		10,000,000
Pepco Holdings LLC [Member] | Successor [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					3,000,000										3,000,000		3,000,000
Pepco Holdings LLC [Member] | Successor [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					18,000,000										18,000,000		18,000,000
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Rate of return on common equity																						10.60%
Public Utilities, Requested Rate Increase (Decrease), Amount																						$ 66,000,000											8,000,000	15,000,000	4,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																						(57,000,000)											10,000,000	1,000,000	(6,000,000)
Regulatory Assets																					348,000,000										348,000,000		348,000,000	371,000,000
Noncurrent regulatory assets																					289,000,000										289,000,000		289,000,000	299,000,000
Public Utilities, Approved Return on Equity, Percentage																							0.00%
Regulatory liabilities																					43,000,000										43,000,000		43,000,000	49,000,000
Business Combination, Integration Related Costs	[2]																																20,000,000	2,000,000
Regulatory Liabilities																					140,000,000										140,000,000		140,000,000	160,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	14,000,000	(12,000,000)	(25,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 12,000,000	$ 3,000,000	$ 8,000,000
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Other Commitment																					86,000,000										86,000,000		$ 86,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount																							$ 2,500,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					4,000,000										4,000,000		4,000,000	$ 3,000,000
Delmarva Power and Light Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					0										0		0	0
Delmarva Power and Light Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					5,000,000										5,000,000		5,000,000	19,000,000
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					3,000,000										3,000,000		3,000,000	11,000,000
Delmarva Power and Light Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																		4,000,000
Delmarva Power and Light Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					2,000,000										2,000,000		2,000,000	4,000,000
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																		$ 39,000,000					63,000,000				$ 15,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																											9.70%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																							(30,000,000)
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase in gas delivery service revenue resulting from rate case settlement or order.																						0.14
Public Utilities, Requested Rate Increase (Decrease), Amount																							22,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																							(10,000,000)
Delmarva Power and Light Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected investment in smart grid infrastructure																						5,000,000
Delmarva Power and Light Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected investment in smart grid infrastructure																						$ 9,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	2,000,000	10,000,000	$ (9,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																														9.55%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	10,000,000	3,000,000	1,000,000
Regulatory Assets																					852,000,000										852,000,000		852,000,000	801,000,000
Noncurrent regulatory assets																					690,000,000										690,000,000		690,000,000	661,000,000
Regulatory liabilities																					11,000,000										11,000,000		11,000,000	15,000,000
Regulatory Liabilities																					31,000,000										31,000,000		31,000,000	44,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	23,000,000	(5,000,000)	(7,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 27,000,000	$ 1,000,000	$ 10,000,000
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Power Plant Output | MW																	661
Capital ProjectFundedByBonds																												$ 375,000,000
CapitalProjectFundedByEntity																												500,000,000
CapitalProjectFundedByAgency																												$ 125,000,000
Other Commitment																					126,000,000										126,000,000		$ 126,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					6,000,000										6,000,000		6,000,000	$ 1,000,000
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					3,000,000										3,000,000		3,000,000	0
Potomac Electric Power Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					8,000,000										8,000,000		8,000,000	16,000,000
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					5,000,000										5,000,000		5,000,000	14,000,000
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					3,000,000										3,000,000		3,000,000	2,000,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																					53,000,000		86,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																					$ (82,000,000)
Public Utilities, Approved Return on Equity, Percentage																					10.60%
Potomac Electric Power Company [Member] | Subsequent Event [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																				$ (77,000,000)
Potomac Electric Power Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Power Plant Output | MW																	650
Potomac Electric Power Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Power Plant Output | MW																	700
Proposed Capital Expenditure																														$ 0.105
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	8,000,000	10,000,000	$ 4,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	14,000,000	(2,000,000)	(3,000,000)
Regulatory Assets																					$ 501,000,000										501,000,000		501,000,000	512,000,000
Noncurrent regulatory assets																					405,000,000										405,000,000		405,000,000	414,000,000
Regulatory liabilities																					25,000,000										25,000,000		25,000,000	18,000,000
Business Combination, Integration Related Costs	[2]																																19,000,000	1,000,000
Regulatory Liabilities																					25,000,000										25,000,000		25,000,000	25,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	6,000,000	(12,000,000)	(7,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 11,000,000	$ 3,000,000	$ 9,000,000
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Other Commitment																					111,000,000										111,000,000		$ 111,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					0										0		0	$ 0
Atlantic City Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					0										0		0	1,000,000
Atlantic City Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					5,000,000										5,000,000		5,000,000	8,000,000
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					4,000,000										4,000,000		4,000,000
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					1,000,000										1,000,000		1,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount																																	(45,000,000)
Public Utilities, Interim Rate Increase (Decrease), Amount																					1,000,000		19,000,000	$ 9,000,000
Atlantic City Electric Company [Member] | Subsequent Event [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Interim Rate Increase (Decrease), Amount																				$ 29,000,000
Deferred Project Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					8,000,000										8,000,000		8,000,000	0
Deferred Project Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Deferred Project Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					8,000,000										8,000,000		8,000,000
Deferred Project Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Rate of return on common equity																													12.95%
Regulatory Assets																					8,000,000								$ 41,000,000		8,000,000		8,000,000	13,000,000
Deferred Project Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under-Recovered Non-Bypassable Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		1,000,000
Smart Meter Related Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					23,000,000										23,000,000		23,000,000
Advanced Metering Infrastructure Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					144,000,000										144,000,000		144,000,000
Advanced Metering Infrastructure Costs [Member] | Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																					3,000,000										3,000,000		3,000,000
Regulatory Assets																					13,000,000										13,000,000		13,000,000
Other Income																					10,000,000
Over-Recovered Natural Gas Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					3,000,000										3,000,000		3,000,000
Abandonment costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					3,000,000										3,000,000		3,000,000
Abandonment costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		3,000,000
Abandonment costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		4,000,000
UnderRecoveredElectricEnergyCosts [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					28,000,000										28,000,000		28,000,000	28,000,000
UnderRecoveredElectricEnergyCosts [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	1,000,000
UnderRecoveredElectricEnergyCosts [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					11,000,000										11,000,000		11,000,000	11,000,000
TransmissionCost [Member] | Commonwealth Edison Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					15,000,000										15,000,000		15,000,000	31,000,000
TransmissionCost [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					4,000,000										4,000,000		4,000,000	12,000,000
TransmissionCost [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000	7,000,000
TransmissionCost [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		5,000,000
TransmissionCost [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					6,000,000										6,000,000		6,000,000	2,000,000
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					188,000,000										188,000,000		188,000,000	189,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net regulatory assets																					188,000,000										188,000,000		188,000,000	189,000,000
Regulatory Assets																					188,000,000										188,000,000		188,000,000	189,000,000
Business Combination, Integration Related Costs																																	11,000,000	11,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					134,000,000										134,000,000		134,000,000	142,000,000
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
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
Under Recovered Distribution Service Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Under Recovered Distribution Service Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					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
Under Recovered Distribution Service Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					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
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					621,000,000										621,000,000		621,000,000	279,000,000
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
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
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					285,000,000										285,000,000		285,000,000	278,000,000
Energy Efficiency And Demand Response Programs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		401,000,000
Energy Efficiency And Demand Response Programs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					335,000,000										335,000,000		335,000,000
Energy Efficiency And Demand Response Programs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					85,000,000										85,000,000		85,000,000	111,000,000
Energy Efficiency And Demand Response Programs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					250,000,000										250,000,000		250,000,000	289,000,000
Energy Efficiency And Demand Response Programs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		$ 0	1,000,000
Non-severance Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		4,000,000
Regulatory Asset, Amortization Period																																	5 years
Pension and Other Postretirement Benefits [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Asset, Amortization Period																																	12 years
Environmental Restoration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					305,000,000										305,000,000		$ 305,000,000	286,000,000
Environmental Restoration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					278,000,000										278,000,000		278,000,000	255,000,000
Environmental Restoration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					26,000,000										26,000,000		26,000,000	30,000,000
Environmental Restoration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000	1,000,000
Environmental Restoration Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Environmental Restoration Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0
Environmental Restoration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Environmental Restoration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Environmental Restoration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Electric Energy And Transmission Costs [Member] | Commonwealth Edison Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		5,000,000
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					701,000,000										701,000,000		701,000,000	399,000,000
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					164,000,000										164,000,000		164,000,000	140,000,000
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					49,000,000										49,000,000		$ 49,000,000	63,000,000
Regulatory Asset, Amortization Period																																	10 years
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																					52,000,000										52,000,000		$ 52,000,000
Regulatory Assets																					230,000,000										230,000,000		230,000,000	196,000,000
Noncurrent regulatory assets																					230,000,000										230,000,000		230,000,000
AMI Expenses [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		267,000,000
AMI Expenses [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					258,000,000										258,000,000		258,000,000
AMI Expenses [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					84,000,000										84,000,000		84,000,000	87,000,000
AMI Expenses [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					174,000,000										174,000,000		174,000,000	180,000,000
AMI Expenses [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					25,000,000										25,000,000		$ 25,000,000	6,000,000
Regulatory Asset, Amortization Period																																	5 years
Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		$ 0	0
Merger Integration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					10,000,000		$ 6,000,000							$ 6,000,000	10,000,000		10,000,000	6,000,000										$ 4,000,000
Merger Integration Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Merger Integration Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					15,000,000										15,000,000		15,000,000
Merger Integration Costs [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	0
Merger Integration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					11,000,000										11,000,000		11,000,000	0
Merger Integration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					89,000,000										89,000,000		89,000,000	84,000,000
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					23,000,000										23,000,000		23,000,000	43,000,000
Business Combination, Integration Related Costs																																	8,000,000	7,000,000
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	1,000,000
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					38,000,000										38,000,000		38,000,000	40,000,000
Under Recovered Energy And Transmission Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		33,000,000
Under Recovered Energy And Transmission Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					28,000,000										28,000,000		28,000,000
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					5,000,000										5,000,000		5,000,000	11,000,000
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					6,000,000										6,000,000		6,000,000	9,000,000
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					17,000,000										17,000,000		17,000,000	13,000,000
Legacy AMI [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					54,000,000										54,000,000		54,000,000
Legacy AMI [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					14,000,000										14,000,000		14,000,000
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
Recoverable Smart Meter Related Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					41,000,000										41,000,000		41,000,000
Recoverable Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					54,000,000										54,000,000		54,000,000	47,000,000
Storm Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					20,000,000										20,000,000		20,000,000	36,000,000
Deferred Income Tax Transmission Related [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					22,000,000										22,000,000		22,000,000	15,000,000
Deferred Income Tax Transmission Related [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					38,000,000										38,000,000		38,000,000	16,000,000
Deferred Income Tax Transmission Related [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					20,000,000										20,000,000		20,000,000	18,000,000
Deferred Income Tax Transmission Related [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					31,000,000										31,000,000		31,000,000	26,000,000
Deferred Income Tax Transmission Related [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					19,000,000										19,000,000		19,000,000	15,000,000
Accelerated Depreciation Costs of Non AMI Meters [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					162,000,000										$ 162,000,000		$ 162,000,000	$ 137,000,000
Non Utility Deferral [Member] | Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Other Regulatory Assets																					10,000,000
Uncollectible deferral Balance [Member] | Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Other Regulatory Assets																					$ 7,000,000

[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] , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, $6 million, $11 million, $4 million, and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information.