Regulatory Matters Regulatory Matters- Narrative (Details) GWh in Millions																																						1 Months Ended		3 Months Ended										9 Months Ended	11 Months Ended	12 Months Ended									60 Months Ended		65 Months Ended
		Dec. 31, 2030	Feb. 05, 2018 USD ($)	Feb. 01, 2018 USD ($)	Jan. 02, 2018 GWh	Jan. 02, 2018 USD ($)	Dec. 19, 2017 USD ($)	Dec. 18, 2017 USD ($)	Nov. 15, 2017 USD ($)	Nov. 07, 2017 USD ($)	Oct. 27, 2017 USD ($)	Oct. 20, 2017 USD ($)	Oct. 18, 2017 USD ($)	Sep. 11, 2017 USD ($)	Sep. 08, 2017 USD ($)	Aug. 24, 2017 USD ($)	Aug. 17, 2017 USD ($)	Jul. 25, 2017 USD ($)	Jul. 24, 2017 USD ($)	Jul. 14, 2017 USD ($)	Jun. 09, 2017 USD ($)	[4]	Apr. 06, 2017 USD ($)	Mar. 30, 2017 USD ($)	Mar. 24, 2017 USD ($)	Mar. 22, 2017 USD ($)	Mar. 08, 2017 USD ($)	Feb. 15, 2017 USD ($)	Feb. 01, 2017 USD ($)	Dec. 17, 2016 USD ($)	Nov. 30, 2016 USD ($)	Nov. 15, 2016 USD ($)	Jul. 29, 2016 USD ($)	May 17, 2016 USD ($)	Feb. 01, 2016 USD ($)	Sep. 10, 2015 USD ($)	Mar. 27, 2015 USD ($)	Jun. 30, 2017 USD ($)	Apr. 30, 2016 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)		Dec. 31, 2016 USD ($)	May 31, 2007	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)		Dec. 31, 2007 USD ($)	Dec. 31, 2023 USD ($)	Nov. 30, 2010 USD ($)	Nov. 30, 2005 USD ($)	Jun. 01, 2019	Jun. 01, 2018	Jul. 21, 2017 USD ($)	Jun. 06, 2017 USD ($)	Jun. 01, 2017	Mar. 24, 2016 USD ($)	Nov. 06, 2015 USD ($)	Dec. 31, 2013 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2011 USD ($)	Aug. 31, 2010 USD ($)	Dec. 31, 2008 USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																									$ 137,000,000													$ 137,000,000
Regulatory Assets																																									9,288,000,000				$ 11,388,000,000					$ 11,388,000,000				9,288,000,000		$ 11,388,000,000
Amortization Rate Stabilization Deferral																																																						(10,000,000)		76,000,000		$ 73,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets	[1]																																								35,000,000													35,000,000
Regulatory Liability, Current																																									523,000,000				602,000,000					602,000,000				523,000,000		602,000,000
Regulatory liabilities																																									9,865,000,000				4,187,000,000					4,187,000,000				9,865,000,000		4,187,000,000
Revenues																																									8,381,000,000	$ 8,769,000,000	$ 7,623,000,000	$ 8,757,000,000	7,875,000,000	$ 9,002,000,000	$ 6,910,000,000	$ 7,573,000,000						$ 33,531,000,000		31,360,000,000		29,447,000,000
Document Period End Date																																																						Dec. 31, 2017
License Costs	[2]																																																									95,000,000
Business Combination, Integration Related Costs	[3]																																																					$ 16,000,000		143,000,000
Regulatory Liabilities																																									10,388,000,000				4,789,000,000					4,789,000,000				10,388,000,000		4,789,000,000
Fair Value, Net Asset (Liability)																																																																					$ 2,400,000,000
Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																									81,000,000													81,000,000
Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									63,000,000													63,000,000
Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									111,000,000				134,000,000					134,000,000				111,000,000		134,000,000
Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									112,000,000													112,000,000
Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									30,000,000				47,000,000					47,000,000				30,000,000		47,000,000
DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									190,000,000													190,000,000
Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									244,000,000				188,000,000					188,000,000				244,000,000		188,000,000
CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									8,000,000				11,000,000					11,000,000				8,000,000		11,000,000
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									953,000,000				1,027,000,000					1,027,000,000				953,000,000		1,027,000,000
AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									640,000,000				701,000,000					701,000,000				640,000,000		701,000,000
Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									82,000,000				89,000,000					89,000,000				82,000,000		89,000,000
Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									45,000,000				25,000,000					25,000,000				45,000,000		25,000,000
COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									5,000,000				8,000,000					8,000,000				5,000,000		8,000,000
Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									596,000,000				621,000,000					621,000,000				596,000,000		621,000,000
Pepco Holdings [Member] | Under funded Benefit Post Retirement Obligation [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									440,000,000				492,000,000					492,000,000				440,000,000		492,000,000
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																									513,000,000													513,000,000
Revenues																																																						4,829,000,000		3,785,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amortization Rate Stabilization Deferral																																																						0		0		0
Revenues																																						$ 12,000,000			4,654,000,000	4,751,000,000	4,174,000,000	4,888,000,000	4,388,000,000	5,035,000,000	3,589,000,000	4,739,000,000						18,466,000,000		17,751,000,000		19,135,000,000
Customer Refund Liability, Noncurrent																																												20,000,000
Purchase Obligation																																																																		$ 235,000,000
License Costs	[2]																																																									0
Business Combination, Integration Related Costs	[3]																																																					22,000,000		37,000,000
Exelon Generation Co L L C [Member] | Conowingo [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License Costs																																																						31,000,000
Exelon Generation Co L L C [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																																							$ 101,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																																									3,000,000													3,000,000
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																																									7,000,000													7,000,000
Exelon Generation Co L L C [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																																																						$ 311,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
SocialCarbonCost																																																						16.50
LowIncomeEnergyAssistanceContributionAnnual																																																						$ 10,000,000
LowIncomeEnergyAssistanceContributionLength																																																						5
Low income sector consumption reduction targets Act 129 Phase II																																																						0.10%
EnergyEfficiencyAnnualCumulativeSavings																																																						6.60%
CumulativeAnnualEnergyEfficiencyGoal | GWh					88
Public Utilities, Requested Rate Increase (Decrease), Amount																					$ (7,000,000)																																	$ 44,000,000	[5]	$ 90,000,000	[5]	$ 68,000,000	[5]
Public Utilities, Approved Equity Capital Structure, Percentage														6.47%																																								8.43%	[6]	8.47%	[6]	8.61%	[6]
Public Utilities, Approved Rate Increase (Decrease), Amount														$ (12,000,000)																																								$ (11,000,000)	[5]	$ (94,000,000)	[5]	$ (86,000,000)	[5]
Public Utilities, Requested Return on Equity, Percentage	[7]																																																					11.50%		11.50%		11.50%
Public Utilities, Approved Return on Equity, Percentage														8.40%
Other Commitment																																									164,000,000													$ 164,000,000
Proposed Capital Expenditure	[5],[8]																																																					0		$ 0		$ 0
Regulatory Assets																																									1,279,000,000				1,167,000,000					1,167,000,000				1,279,000,000		1,167,000,000
Amortization Rate Stabilization Deferral																																																						0		0		0
Amount of Impairment to Carrying Amount of Regulatory Assets																																									3,000,000													3,000,000
Regulatory Liability, Current																																									249,000,000				329,000,000					329,000,000				249,000,000		329,000,000
Regulatory liabilities																																									6,328,000,000				3,369,000,000					3,369,000,000				6,328,000,000		3,369,000,000
Revenues																																									1,309,000,000	1,571,000,000	1,357,000,000	1,298,000,000	1,223,000,000	1,497,000,000	1,286,000,000	1,249,000,000						5,536,000,000		5,254,000,000		4,905,000,000
Purchase Obligation																																																																		$ 170,000,000
License Costs	[2]																																																									0
Business Combination, Integration Related Costs	[3],[9]																																																					1,000,000		(6,000,000)
Regulatory Liabilities																																									6,577,000,000				3,698,000,000					3,698,000,000				6,577,000,000		3,698,000,000
DecouplingImpactOnOperatingRevenuesAndRegulatoryAssets																																																						$ 32,000,000
RenewableEnergyRetailLoad																																																																				50.00%
Commonwealth Edison Co [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%
RenewableEnergyRetailLoad																																																																100.00%	75.00%
Tax Savings From Tax Cuts and Jobs Act				$ 201,000,000
Commonwealth Edison Co [Member] | Energy Related Derivative [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Term of contract																																																						20 years
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																																						$ 78,000,000		$ 134,000,000		$ 85,000,000
Public Utilities, Approved Equity Capital Structure, Percentage																																																						6.45%		6.69%		7.02%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																										$ (18,000,000)																												$ 96,000,000		$ 127,000,000	[10]	$ (67,000,000)
Public Utilities, Approved Rate Increase (Decrease), Amount																																																						$ (18,000,000)		$ 7,000,000		$ 152,000,000
Public Utilities, Requested Return on Equity, Percentage																																																						8.40%		8.64%		9.14%
Public Utilities, Approved Return on Equity, Percentage	[11]																																																					8.34%		8.59%		9.09%
Public Utilities, Requested Equity Capital Structure, Percentage																																																						6.47%		6.71%		7.05%
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
FutureEnergyEfficiencySpending																																																						$ 350,000,000
EnergyEfficiencyROEAdjustment																																																						20000.00%
Renewable Energy Resources Cumulatively Increase																																																						13.00%
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
FutureEnergyEfficiencySpending																																																						$ 400,000,000
ResidentialCustomerRateIncrease																																																						0.25
CommercialAndIndustrialCustomerRateIncrease																																																						1.30%
Amount of Impairment to Carrying Amount of Regulatory Assets																																									41,000,000													$ 41,000,000
Renewable Energy Resources Cumulatively Increase																																																						25.00%
Commonwealth Edison Co [Member] | Maximum [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																																						$ 96,000,000		$ 138,000,000		$ (50,000,000)
Commonwealth Edison Co [Member] | Reductions Under TCJA [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									553,000,000													553,000,000
Commonwealth Edison Co [Member] | ACPpayment member [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									41,000,000													41,000,000
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									484,000,000													484,000,000
Commonwealth Edison Co [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																									10,000,000													10,000,000
Regulatory liabilities																																									20,000,000													20,000,000
Regulatory Liabilities																																									63,000,000													63,000,000
Restricted Cash																																									62,000,000													62,000,000
Commonwealth Edison Co [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									47,000,000				60,000,000					60,000,000				47,000,000		60,000,000
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																									14,000,000				30,000,000					30,000,000				14,000,000		30,000,000
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									33,000,000				30,000,000					30,000,000				33,000,000		30,000,000
Commonwealth Edison Co [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									112,000,000													112,000,000
Commonwealth Edison Co [Member] | Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
Commonwealth Edison Co [Member] | EDArefund Member [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									80,000,000													80,000,000
Commonwealth Edison Co [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0													0
Commonwealth Edison Co [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									21,000,000													21,000,000
Commonwealth Edison Co [Member] | Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									244,000,000				188,000,000					188,000,000				244,000,000		188,000,000
Commonwealth Edison Co [Member] | Electric distribution formula rate | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									186,000,000				134,000,000					134,000,000				186,000,000		134,000,000
Commonwealth Edison Co [Member] | CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													22,000,000					22,000,000						22,000,000
Commonwealth Edison Co [Member] | AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									155,000,000				164,000,000					164,000,000				155,000,000		164,000,000
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									58,000,000				54,000,000					54,000,000				58,000,000		54,000,000
Commonwealth Edison Co [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									6,000,000				23,000,000					23,000,000				6,000,000		23,000,000
Business Combination, Integration Related Costs																																																								8,000,000
Commonwealth Edison Co [Member] | TransmissionCost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													15,000,000					15,000,000						15,000,000
Commonwealth Edison Co [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Commonwealth Edison Co [Member] | COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Commonwealth Edison Co [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																				$ 127,000,000	$ 190,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage																																					10.95%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																																						22,000,000
Other Commitment																																									53,000,000													53,000,000
Regulatory Assets																																									410,000,000				1,710,000,000					1,710,000,000				410,000,000		1,710,000,000
Amortization Rate Stabilization Deferral																																																						0		0		0
Regulatory Liability, Current																																									141,000,000				127,000,000					127,000,000				141,000,000		127,000,000
Regulatory liabilities																																									549,000,000				517,000,000					517,000,000				549,000,000		517,000,000
Revenues																																									729,000,000	715,000,000	630,000,000	796,000,000	701,000,000	788,000,000	664,000,000	841,000,000						2,870,000,000		2,994,000,000		3,032,000,000
License Costs	[2]																																																									0
Business Combination, Integration Related Costs	[3]																																																					4,000,000		5,000,000
Regulatory Liabilities																																									690,000,000				644,000,000					644,000,000				$ 690,000,000		644,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																																																						11.00%
PECO Energy Co [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													$ 0
PECO Energy Co [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									60,000,000				56,000,000					56,000,000				60,000,000		56,000,000
PECO Energy Co [Member] | DSP Program costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									36,000,000				34,000,000					34,000,000				36,000,000		34,000,000
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									12,000,000													12,000,000
PECO Energy Co [Member] | Over-Recovered Electric Transmission Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									12,000,000				4,000,000					4,000,000				12,000,000		4,000,000
PECO Energy Co [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																													8,000,000					8,000,000						8,000,000
PECO Energy Co [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
PECO Energy Co [Member] | Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
PECO Energy Co [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0													0
PECO Energy Co [Member] | Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
PECO Energy Co [Member] | CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									8,000,000				11,000,000					11,000,000				8,000,000		11,000,000
PECO Energy Co [Member] | AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									36,000,000				49,000,000					49,000,000				$ 36,000,000		49,000,000
Regulatory Asset, Amortization Period																																																						10 years
PECO Energy Co [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									1,000,000				0					0				$ 1,000,000		0
PECO Energy Co [Member] | Under-Recovered Non-Bypassable Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													10,000,000					10,000,000						10,000,000
PECO Energy Co [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
PECO Energy Co [Member] | COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
PECO Energy Co [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									1,000,000				1,000,000					1,000,000				1,000,000		1,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																																						$ 31,000,000	[5]	$ 12,000,000	[5]	$ 0	[5]		$ 242,000,000
Public Utilities, Approved Equity Capital Structure, Percentage	[6]																																																					7.47%		8.09%		8.46%
Public Utilities, Approved Rate Increase (Decrease), Amount	[5]																																																					$ (26,000,000)		$ (28,000,000)		$ (10,000,000)
Public Utilities, Requested Return on Equity, Percentage	[7]																																																					10.50%		10.50%		11.30%
Other Commitment																																									118,000,000													$ 118,000,000
Proposed Capital Expenditure																																																						(8,000,000)	[5],[8]	$ 13,000,000	[5],[8]	$ 13,000,000	[5],[8]		$ 963,000,000
Regulatory Assets																																									571,000,000				712,000,000					712,000,000				571,000,000		712,000,000
Rate Cap Imposed On Public Utility Subsidiary																																																			15.00%
Deferred Purchased Power Costs																																																												$ 306,000,000
Amortization Rate Stabilization Deferral																																																						7,000,000		81,000,000		73,000,000
Estimated number of smart meters to be installed																																																																										2,000,000
Total smart grid smart meter investment grant awarded																																																																										$ 480,000,000
Doe Reimbursements																																																																										$ 200,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets																																									5,000,000													5,000,000
Captial and OM estimates current year																																									136,000,000													136,000,000
Regulatory Liability, Current																																									62,000,000				50,000,000					50,000,000				62,000,000		50,000,000
Deferred Costs, Noncurrent																																																																								$ 8,000,000	$ 16,000,000
Regulatory liabilities																																									1,101,000,000				110,000,000					110,000,000				1,101,000,000		110,000,000
Revenues																																									813,000,000	738,000,000	674,000,000	951,000,000	812,000,000	812,000,000	680,000,000	929,000,000						3,176,000,000		3,233,000,000		3,135,000,000
Customer Refund Liability, Noncurrent																																																																						$ 30,000,000
License Costs	[2]																																																									0
Business Combination, Integration Related Costs	[3],[9]																																																					4,000,000		(1,000,000)
Site Contingency, Recovery from Third Party of Environmental Remediation Cost																																																														$ 1,000,000	$ 5,000,000
Regulatory Liabilities																																									1,163,000,000				160,000,000					160,000,000				1,163,000,000		160,000,000
Baltimore Gas and Electric Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act				103,000,000
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
Projected Investment In Smartmeters																																																																						104,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	$ (44,000,000)
Public Utilities, Requested Return on Equity, Percentage																																	9.75%
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act				72,000,000
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
Projected Investment In Smartmeters																																																																						$ 37,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	$ (48,000,000)
Public Utilities, Requested Return on Equity, Percentage																																	9.65%
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act				31,000,000
Baltimore Gas and Electric Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																									22,000,000													22,000,000
Baltimore Gas and Electric Company [Member] | Reductions Under TCJA [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									174,000,000													174,000,000
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									137,000,000													137,000,000
Baltimore Gas and Electric Company [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Baltimore Gas and Electric Company [Member] | Stride Program [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									1,000,000													1,000,000
Baltimore Gas and Electric Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													9,000,000					9,000,000						9,000,000
Regulatory Liabilities																																									0				0					0				0		0
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																													3,000,000					3,000,000						3,000,000
Baltimore Gas and Electric Company [Member] | Under-recovered revenue decoupling
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									4,000,000				2,000,000					2,000,000				4,000,000		2,000,000
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									10,000,000				1,000,000					1,000,000				10,000,000		1,000,000
Baltimore Gas and Electric Company [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Baltimore Gas and Electric Company [Member] | Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
Baltimore Gas and Electric Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0													0
Baltimore Gas and Electric Company [Member] | Under-Recovered Natural Gas Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									8,000,000				3,000,000					3,000,000				8,000,000		3,000,000
Baltimore Gas and Electric Company [Member] | Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Baltimore Gas and Electric Company [Member] | CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													38,000,000					38,000,000						38,000,000
Baltimore Gas and Electric Company [Member] | AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									214,000,000				230,000,000					230,000,000				214,000,000		230,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets																																															52,000,000
Baltimore Gas and Electric Company [Member] | Unamortized AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									129,000,000				144,000,000					144,000,000				129,000,000		144,000,000
Baltimore Gas and Electric Company [Member] | Legacy AMI [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									53,000,000				54,000,000		56,000,000			54,000,000				53,000,000		54,000,000
Baltimore Gas and Electric Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									23,000,000				38,000,000					38,000,000				23,000,000		38,000,000
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									7,000,000				4,000,000					4,000,000				7,000,000		4,000,000
Baltimore Gas and Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									5,000,000				28,000,000					28,000,000				5,000,000		28,000,000
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									3,000,000													3,000,000
Baltimore Gas and Electric Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									6,000,000				10,000,000					10,000,000				6,000,000		10,000,000																$ 4,000,000
Baltimore Gas and Electric Company [Member] | Non-severance Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																																																							$ 4,000,000
Baltimore Gas and Electric Company [Member] | PHI Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									4,000,000				6,000,000					6,000,000				4,000,000		6,000,000
Baltimore Gas and Electric Company [Member] | COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									32,000,000				32,000,000					32,000,000				32,000,000		32,000,000
Baltimore Gas and Electric Company [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									285,000,000				285,000,000					285,000,000				285,000,000		285,000,000
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																												444,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets	[1]																																								27,000,000													27,000,000
Business Combination, Integration Related Costs	[3],[9]																																																					(6,000,000)		28,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									3,047,000,000				3,504,000,000					3,504,000,000				3,047,000,000		3,504,000,000
Amortization Rate Stabilization Deferral																																																		(5,000,000)				(17,000,000)
Regulatory Liability, Current																																									56,000,000				79,000,000					79,000,000				56,000,000		79,000,000
Regulatory liabilities																																									1,872,000,000				158,000,000					158,000,000				1,872,000,000		158,000,000
Revenues																																									1,121,000,000	1,310,000,000	1,074,000,000	1,175,000,000	1,078,000,000	1,394,000,000	1,066,000,000	105,000,000	[12]	3,643,000,000				4,679,000,000
Business Combination, Integration Related Costs	[9],[13]																																																	69,000,000				(18,000,000)
Regulatory Liabilities																																									1,928,000,000				237,000,000					237,000,000				1,928,000,000		237,000,000
Pepco Holdings LLC [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																									18,000,000													18,000,000
Pepco Holdings LLC [Member] | Renewable portfolio standards costs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Pepco Holdings LLC [Member] | Energy and transmission programs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									4,000,000				18,000,000					18,000,000				4,000,000		18,000,000
Pepco Holdings LLC [Member] | Zero emission credit costs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Pepco Holdings LLC [Member] | Pension and other postretirement benefits | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
Pepco Holdings LLC [Member] | DC PLUG charge | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									190,000,000													190,000,000
Pepco Holdings LLC [Member] | Electric distribution formula rate | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Pepco Holdings LLC [Member] | CAP arrearage | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Pepco Holdings LLC [Member] | AMI programs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									235,000,000				258,000,000					258,000,000				235,000,000		258,000,000
Pepco Holdings LLC [Member] | Energy and transmission programs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									52,000,000				28,000,000					28,000,000				52,000,000		28,000,000
Pepco Holdings LLC [Member] | Merger integration costs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									39,000,000				15,000,000					15,000,000				39,000,000		15,000,000
Pepco Holdings LLC [Member] | COPCO acquisition adjustment | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									5,000,000				8,000,000					8,000,000				5,000,000		8,000,000
Pepco Holdings LLC [Member] | Energy efficiency and demand response programs | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									310,000,000				335,000,000					335,000,000				310,000,000		335,000,000
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																									315,000,000													315,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[5]																																																					$ 5,000,000		$ 2,000,000		$ 10,000,000
Public Utilities, Approved Equity Capital Structure, Percentage	[6]																																																					7.92%		7.88%		8.36%
Public Utilities, Approved Rate Increase (Decrease), Amount	[5]																																																					$ (20,000,000)		$ 23,000,000		$ (5,000,000)
Public Utilities, Requested Return on Equity, Percentage	[7]																																																					10.50%		10.50%		11.30%
Other Commitment																																									86,000,000													$ 86,000,000
Projected Capital Expenditures																																										500,000,000
Regulatory Assets																																									891,000,000				852,000,000					852,000,000				891,000,000		$ 852,000,000
Amortization Rate Stabilization Deferral																																																						(17,000,000)		(12,000,000)		$ 1,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets																																									14,000,000													14,000,000
Regulatory Liability, Current																																									3,000,000				11,000,000					11,000,000				3,000,000		11,000,000
Regulatory liabilities																																									829,000,000				20,000,000					20,000,000				829,000,000		20,000,000
Revenues																																									510,000,000	604,000,000	$ 514,000,000	530,000,000	491,000,000	635,000,000	509,000,000	551,000,000						2,158,000,000		2,186,000,000		2,129,000,000
License Costs	[2]																																																									0
Regulatory Liabilities																																									832,000,000				31,000,000					31,000,000				$ 832,000,000		31,000,000
Alternative Net Capital Requirement																																										250,000,000
Capital ProjectFundedByBonds																																									187,000,000	187,500,000			3,000,000
CapitalProjectFundedByAgency																																										62,500,000
Potomac Electric Power Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Capital ProjectFundedByBonds																																																					$ 27,500,000
CapitalProjectFundedByAgency																																																				$ 60,000,000
Tax Savings From Tax Cuts and Jobs Act			$ 31,000,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			11,000,000			$ 41,000,000	$ 66,000,000																		$ 69,000,000																						86,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage						10.10%										10.10%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																$ 67,000,000													$ 77,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount											$ (32,000,000)	$ (34,000,000)						$ (37,000,000)														$ (53,000,000)
Public Utilities, Requested Return on Equity, Percentage							10.10%
Public Utilities, Approved Return on Equity, Percentage												9.50%						9.50%											10.60%			9.55%
TaxAdjustmentIncludedInPublicUtilitiesRequestedRateIncreaseDecreaseAmount																18,000,000
Potomac Electric Power Company [Member] | Electric Distribution [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act				$ 39,000,000
Potomac Electric Power Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Return on Equity, Percentage																																																						10.50%
Amount of Impairment to Carrying Amount of Regulatory Assets																																									8,000,000													$ 8,000,000
Potomac Electric Power Company [Member] | Reductions Under TCJA [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									161,000,000													161,000,000
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									147,000,000													147,000,000
Potomac Electric Power Company [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Potomac Electric Power Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				8,000,000					8,000,000				0		8,000,000
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																													3,000,000					3,000,000						3,000,000
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																													5,000,000					5,000,000						5,000,000
Potomac Electric Power Company [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Potomac Electric Power Company [Member] | Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
Potomac Electric Power Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									190,000,000													190,000,000
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInDCServiceTerritory [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									9,000,000													9,000,000
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									11,000,000													11,000,000
Potomac Electric Power Company [Member] | Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Potomac Electric Power Company [Member] | CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Potomac Electric Power Company [Member] | Advanced Metering Infrastructure Costs [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													13,000,000					13,000,000						13,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets																																													3,000,000					3,000,000						3,000,000
Other Income																																																								10,000,000
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													31,000,000					31,000,000						31,000,000
Potomac Electric Power Company [Member] | AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									158,000,000				174,000,000					174,000,000				158,000,000		174,000,000
Potomac Electric Power Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									11,000,000				6,000,000					6,000,000				11,000,000		6,000,000
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									3,000,000													3,000,000
Potomac Electric Power Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									8,000,000													8,000,000
Potomac Electric Power Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									20,000,000				11,000,000					11,000,000				20,000,000		11,000,000
Potomac Electric Power Company [Member] | COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Potomac Electric Power Company [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									229,000,000				250,000,000					250,000,000				229,000,000		250,000,000
Potomac Electric Power Company [Member] | Pepco Holdings [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																		$ 26,000,000
Potomac Electric Power Company [Member] | Pepco Holdings [Member] | Minimum [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																		6,000,000
Potomac Electric Power Company [Member] | Pepco Holdings [Member] | Maximum [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																		$ 7,000,000
Potomac Electric Power Company [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																									120,000,000													120,000,000
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[5]																																																					$ 6,000,000		$ 8,000,000		$ 15,000,000
Public Utilities, Approved Equity Capital Structure, Percentage	[6]																																																					7.16%		7.21%		7.80%
Public Utilities, Interim Rate Increase (Decrease), Amount																	$ 2,500,000																													2,500,000
Public Utilities, Approved Rate Increase (Decrease), Amount	[5]																																																					$ (14,000,000)		$ 14,000,000		$ (12,000,000)
Public Utilities, Requested Return on Equity, Percentage	[7]																																																					10.50%		10.50%		11.30%
Public Utilities, Approved Return on Equity, Percentage																	0.00%																										0.00%
Other Commitment																																									27,000,000													$ 27,000,000
Regulatory Assets																																									314,000,000				348,000,000					348,000,000				314,000,000		$ 348,000,000
Amortization Rate Stabilization Deferral																																																						0		2,000,000		$ (3,000,000)
Amount of Impairment to Carrying Amount of Regulatory Assets																																									6,000,000													6,000,000
Regulatory Liability, Current																																									42,000,000				43,000,000					43,000,000				42,000,000		43,000,000
Regulatory liabilities																																									593,000,000				97,000,000					97,000,000				593,000,000		97,000,000
Revenues																																									330,000,000	327,000,000	$ 282,000,000	362,000,000	303,000,000	331,000,000	281,000,000	362,000,000						1,300,000,000		1,277,000,000		1,302,000,000
Customer Refund Liability, Noncurrent																																																																			$ 5,000,000
License Costs	[2]																																																									0
Business Combination, Integration Related Costs	[3],[9]																																																					(7,000,000)		20,000,000
Regulatory Liabilities																																									635,000,000				140,000,000					140,000,000				635,000,000		140,000,000
Delmarva Power and Light Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act			26,000,000
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount													$ 31,000,000				$ 24,000,000		$ 27,000,000															$ 63,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage									10.10%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 19,300,000																		$ 60,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount								$ (13,000,000)																			$ (31,500,000)	$ (38,000,000)		$ (30,000,000)																										(32,000,000)
Public Utilities, Approved Return on Equity, Percentage								9.50%																			9.70%	9.60%
Projected Capital Expenditures																												$ 5,000,000
Delmarva Power and Light Company [Member] | Electric Distribution [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act			19,000,000																																					$ 13,000,000
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount										$ 11,000,000							$ 13,000,000																	$ 22,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																							$ (4,900,000)
Public Utilities, Approved Return on Equity, Percentage																							9.70%							1000000000.00%
Delmarva Power and Light Company [Member] | Gas Distribution [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act			$ 7,000,000
Delmarva Power and Light Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																									7,000,000													7,000,000
Delmarva Power and Light Company [Member] | Reductions Under TCJA [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									160,000,000													160,000,000
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									148,000,000													148,000,000
Delmarva Power and Light Company [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Delmarva Power and Light Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									1,000,000				5,000,000					5,000,000				1,000,000		5,000,000
Delmarva Power and Light Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																													2,000,000					2,000,000						2,000,000
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																													3,000,000					3,000,000						3,000,000
Delmarva Power and Light Company [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Delmarva Power and Light Company [Member] | Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
Delmarva Power and Light Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0													0
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									4,000,000													4,000,000
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInDelaware [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									5,000,000													5,000,000
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandAndDelaware [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									1,000,000													1,000,000
Delmarva Power and Light Company [Member] | Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Delmarva Power and Light Company [Member] | CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													20,000,000					20,000,000						20,000,000
Delmarva Power and Light Company [Member] | AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									77,000,000				84,000,000					84,000,000				77,000,000		84,000,000
Delmarva Power and Light Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									15,000,000				5,000,000					5,000,000				15,000,000		5,000,000
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									8,000,000				1,000,000					1,000,000				8,000,000		1,000,000
Delmarva Power and Light Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									7,000,000				4,000,000					4,000,000				7,000,000		4,000,000
Delmarva Power and Light Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									10,000,000				4,000,000					4,000,000				10,000,000		4,000,000
Delmarva Power and Light Company [Member] | COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									5,000,000				8,000,000					8,000,000				5,000,000		8,000,000																			$ 41,000,000
Delmarva Power and Light Company [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									81,000,000				85,000,000					85,000,000				81,000,000		85,000,000
Delmarva Power and Light Company [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																									84,000,000													84,000,000
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[5]																																																					$ 20,000,000		$ 8,000,000		$ 10,000,000
Public Utilities, Approved Equity Capital Structure, Percentage	[6]																																																					8.02%		7.83%		8.51%
Public Utilities, Approved Rate Increase (Decrease), Amount	[5]																																																					$ (42,000,000)		$ 6,000,000		$ (12,000,000)
Public Utilities, Requested Return on Equity, Percentage	[7]																																																					10.50%		10.50%		11.30%
Other Commitment																																									121,000,000													$ 121,000,000
Projected Capital Expenditures																$ 79,000,000
Proposed Capital Expenditure																													$ 29,000,000						$ 9,000,000								32,000,000				19,000,000
Regulatory Assets																																									430,000,000				501,000,000					501,000,000				430,000,000		$ 501,000,000
Amortization Rate Stabilization Deferral																																																						0		0		$ 0
Amount of Impairment to Carrying Amount of Regulatory Assets																																									7,000,000													7,000,000
Regulatory Liability, Current																																									11,000,000				25,000,000					25,000,000				11,000,000		25,000,000
Regulatory liabilities																																									411,000,000				0					0				411,000,000		0
Revenues																																									271,000,000	$ 370,000,000	$ 270,000,000	$ 275,000,000	275,000,000	$ 421,000,000	$ 270,000,000	$ 291,000,000						1,186,000,000		1,257,000,000		1,295,000,000
License Costs	[2]																																																									$ 0
Business Combination, Integration Related Costs	[3],[9]																																																					(6,000,000)		19,000,000
Regulatory Liabilities																																									422,000,000				25,000,000					25,000,000				422,000,000		25,000,000
Atlantic City Electric Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																								$ 23,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																								$ 70,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage																				10.10%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																				$ 73,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount															$ (43,000,000)																$ (1,000,000)
Public Utilities, Approved Return on Equity, Percentage															9.60%
Atlantic City Electric Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																									3,000,000													3,000,000
Atlantic City Electric Company [Member] | Reductions Under TCJA [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									152,000,000													152,000,000
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																									147,000,000													147,000,000
Atlantic City Electric Company [Member] | Renewable portfolio standards costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Atlantic City Electric Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									3,000,000				5,000,000					5,000,000				3,000,000		5,000,000
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																													1,000,000					1,000,000						1,000,000
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current																																													4,000,000					4,000,000						4,000,000
Atlantic City Electric Company [Member] | Zero emission credit costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0													0
Atlantic City Electric Company [Member] | Pension and other postretirement benefits
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																									0				0					0				0		0
Atlantic City Electric Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0													0
Atlantic City Electric Company [Member] | Electric distribution formula rate
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Atlantic City Electric Company [Member] | Uncollectible deferral Balance [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Other Regulatory Assets																															7,000,000
Atlantic City Electric Company [Member] | Non Utility Deferral [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Other Regulatory Assets																															$ 10,000,000
Atlantic City Electric Company [Member] | CAP arrearage
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																													19,000,000					19,000,000						19,000,000
Atlantic City Electric Company [Member] | AMI programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Atlantic City Electric Company [Member] | Energy and transmission programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									26,000,000				17,000,000					17,000,000				26,000,000		17,000,000
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									11,000,000				6,000,000					6,000,000				11,000,000		6,000,000
Atlantic City Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									15,000,000				11,000,000					11,000,000				15,000,000		11,000,000
Atlantic City Electric Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									9,000,000				0					0				9,000,000		0
Atlantic City Electric Company [Member] | COPCO acquisition adjustment
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				0					0				0		0
Atlantic City Electric Company [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																									0				$ 0					$ 0				0		$ 0
Atlantic City Electric Company [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																									$ 111,000,000													$ 111,000,000

[1] Exelon reflects the consolidated regulatory asset impairments of ComEd, BGE, Pepco, DPL and ACE, and PHI reflects the consolidated regulatory asset impairments of Pepco, DPL and ACE.

[2] Relates to a long-term software license agreement entered into on May 30, 2015. Exelon is required to make payments starting August of 2015 through May of 2024. See Note 13 - Debt and Credit Agreements.

[3] 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.

[4] Reflects higher projected PJM capacity revenues compared to projected energy efficiency costs.

[5] The time period for any challenges to the annual transmission formula rate update flings expired with no challenges submitted

[6] Represents to the weighted average debt and equity return on transmission rate bases.

[7] As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50%, inclusive of a 50-basis-point incentive adder for being a member of a RTO, 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 RTO.

[8] 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.

[9] (b)For the year ended December 31, 2017, includes deferrals of previously incurred integration costs to achieve distribution synergies related to the PHI acquisition of $24 million, $8 million, $8 million, and $8 million incurred at PHI, Pepco, DPL, and ACE, respectively, that have been recorded as a regulatory asset for anticipated recovery. For the year ended December 31, 2016, includes deferrals of previously incurred integration costs to achieve distribution synergies related to the PHI acquisition of $8 million, $6 million, $11 million, and $4 million incurred at ComEd, BGE, Pepco, and DPL, respectively, that have been recorded as a regulatory asset for anticipated recovery. For the Successor period March 24, 2016 to December 31, 2016, includes deferrals of previously incurred integration costs to achieve distribution synergies related to the PHI acquisition of $16 million incurred at PHI that have been recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information.

[10] On March 22, 2017, the ICC issued an order approving ComEd's proposal to reduce the 2016 revenue requirement by $18 million, which was reflected in customer rates beginning in April 2017. This reduction is not reflected in the 2016 revenue requirement amounts above.

[11] Includes a reduction of 6 basis points in 2017 and 5 basis points in 2016 and 2015 for a reliability performance metric penalty.

[12] Amounts for March 31, 2016 reflect the PHI Successor activity for the period March 24, 2016 to March 31, 2016.

[13] (a)Amounts shown reflect the final purchase price allocation and the correction of a reporting error identified and corrected in the second quarter of 2016. The error had resulted in a gross up of certain assets and liabilities related to legacy PHI intercompany and income tax receivable and payable balances.