Regulatory Matters Regulatory Matters- Narrative (Details)																													1 Months Ended	3 Months Ended								7 Months Ended	9 Months Ended		12 Months Ended					48 Months Ended	60 Months Ended	78 Months Ended
		Jan. 15, 2019 USD ($)	Jan. 04, 2019 USD ($)	Dec. 20, 2018 USD ($)	Dec. 04, 2018 USD ($)	Nov. 19, 2018 USD ($)	Sep. 07, 2018 USD ($)	Aug. 21, 2018 USD ($)	Jul. 01, 2018 USD ($)	Jun. 27, 2018 USD ($)	Jun. 08, 2018 USD ($)	Apr. 20, 2018 USD ($)	[7]	Apr. 17, 2018 USD ($)	[7]	Apr. 16, 2018 USD ($)	Mar. 29, 2018 USD ($)	Mar. 08, 2018 USD ($)	[7]	Mar. 02, 2018 USD ($)	Feb. 09, 2018 USD ($)		Feb. 06, 2018 USD ($)	Jan. 31, 2018 USD ($)	Jan. 18, 2018 USD ($)	Dec. 19, 2017 USD ($)	Dec. 18, 2017 USD ($)	Nov. 16, 2017 USD ($)	Apr. 30, 2016 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)		Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Jul. 21, 2017 USD ($)	Aug. 31, 2010 USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																														$ 127,000,000											$ 127,000,000
Regulatory Assets																														9,459,000,000				$ 9,288,000,000				$ 9,288,000,000			9,459,000,000		$ 9,288,000,000
Amortization Rate Stabilization Deferral																																									14,000,000		(10,000,000)		$ 76,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets																																		35,000,000				35,000,000					35,000,000
Regulatory Liability, Current																														644,000,000				523,000,000				523,000,000			644,000,000		523,000,000
Regulatory liabilities, noncurrent																														9,559,000,000				9,865,000,000				9,865,000,000			9,559,000,000		9,865,000,000
Revenues																														8,814,000,000	$ 9,403,000,000	$ 8,076,000,000	$ 9,693,000,000	8,384,000,000	$ 8,768,000,000	$ 7,665,000,000	$ 8,747,000,000				35,985,000,000		33,565,000,000		31,366,000,000
Business Combination, Integration Related Costs																																									7,000,000	[1]	16,000,000	[1]	143,000,000
Regulatory Liabilities																														10,203,000,000				10,388,000,000				10,388,000,000			10,203,000,000		10,388,000,000
Accounts Payable, Current																														3,800,000,000				3,532,000,000				3,532,000,000			3,800,000,000		3,532,000,000
Payments to Acquire Property, Plant, and Equipment																																									7,594,000,000		7,584,000,000		8,553,000,000
PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																176,000,000
DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														159,000,000				190,000,000				190,000,000			159,000,000		190,000,000
Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		758,000,000				758,000,000					758,000,000
Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														328,000,000				223,000,000				223,000,000			328,000,000		223,000,000
Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														193,000,000				47,000,000				47,000,000			193,000,000		47,000,000
Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														42,000,000				45,000,000				45,000,000			42,000,000		45,000,000
Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														545,000,000				596,000,000				596,000,000			545,000,000		596,000,000
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																																									4,670,000,000		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																														5,069,000,000	5,278,000,000	4,579,000,000	5,512,000,000	4,657,000,000	4,750,000,000	4,216,000,000	4,878,000,000				20,437,000,000		18,500,000,000		17,757,000,000
Purchase Obligation																																																	$ 235,000,000
Business Combination, Integration Related Costs																																									5,000,000	[1]	22,000,000	[1]	37,000,000
Accounts Payable, Current																														1,847,000,000				1,773,000,000				1,773,000,000			1,847,000,000		1,773,000,000
Payments to Acquire Property, Plant, and Equipment																																									2,242,000,000		2,259,000,000		3,078,000,000
Exelon Generation Co L L C [Member] | Conowingo [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License Costs																																									37,000,000
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] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current	[2]																															41,000,000
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																																									438,000,000		$ 311,000,000
Other Revenue, Net																																						150,000,000			373,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
SocialCarbonCost																																											16.50
Public Utilities, Requested Rate Increase (Decrease), Amount	[3]																																								$ (44,000,000)
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint																																									55.00%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[3],[4]																																								$ (26,000,000)
Public Utilities, Approved Return on Equity, Percentage	[3],[5]																																								11.50%
Regulatory Assets																																		1,279,000,000				1,279,000,000					$ 1,279,000,000
Amortization Rate Stabilization Deferral																																									$ 0		0		0
Amount of Impairment to Carrying Amount of Regulatory Assets																																		3,000,000				3,000,000					3,000,000
Regulatory Liability, Current																														293,000,000				249,000,000				249,000,000			293,000,000		249,000,000
Regulatory liabilities, noncurrent																														6,050,000,000				6,328,000,000				6,328,000,000			6,050,000,000		6,328,000,000
Revenues																														1,373,000,000	1,598,000,000	1,398,000,000	1,512,000,000	1,309,000,000	1,571,000,000	1,357,000,000	1,298,000,000				5,882,000,000		5,536,000,000		5,254,000,000
Purchase Obligation																																																	$ 170,000,000
Business Combination, Integration Related Costs																																									0	[1],[6]	1,000,000	[1],[6]	(6,000,000)
Regulatory Liabilities																														6,343,000,000				6,577,000,000				6,577,000,000			6,343,000,000		6,577,000,000
Prior Year Revenue Adjustment	[3]																																								18,000,000
Tax Savings From Tax Cuts and Jobs Act																									$ 201,000,000
Accounts Payable, Current																														607,000,000				568,000,000				568,000,000			607,000,000		568,000,000
Payments to Acquire Property, Plant, and Equipment																																									2,126,000,000		2,250,000,000		2,734,000,000
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																									(58,000,000)
Public Utilities, Approved Rate Increase (Decrease), Amount																																											34,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[7]				$ (24,000,000)											$ (23,000,000)
Public Utilities, Requested Equity Capital Structure, Percentage					8.69%
Commonwealth Edison Co [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																									69,000,000
Commonwealth Edison Co [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																0
Commonwealth Edison Co [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0				0					0
Commonwealth Edison Co [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0				0					0
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														136,000,000				155,000,000				155,000,000			136,000,000		155,000,000
Commonwealth Edison Co [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0				0					0
Commonwealth Edison Co [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		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
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																									22,000,000
Regulatory Assets																																		410,000,000				410,000,000					410,000,000
Amortization Rate Stabilization Deferral																																									0		0		0
Regulatory Liability, Current																														175,000,000				141,000,000				141,000,000			175,000,000		141,000,000
Regulatory liabilities, noncurrent																														421,000,000				549,000,000				549,000,000			421,000,000		549,000,000
Revenues																														765,000,000	757,000,000	653,000,000	866,000,000	729,000,000	715,000,000	630,000,000	796,000,000				3,038,000,000		2,870,000,000		2,994,000,000
Business Combination, Integration Related Costs																																									1,000,000	[1]	4,000,000	[1]	5,000,000
Regulatory Liabilities																														596,000,000				690,000,000				690,000,000			$ 596,000,000		690,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																																									11.00%
Prior Year Revenue Adjustment																																							$ 6,000,000
Tax Savings From Tax Cuts and Jobs Act																	$ 71,000,000
Accounts Payable, Current																														370,000,000				370,000,000				370,000,000			$ 370,000,000		370,000,000
Payments to Acquire Property, Plant, and Equipment																																									849,000,000		732,000,000		686,000,000
PECO Energy Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[7]																$ 82,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[7]			$ 25,000,000
PECO Energy Co [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act									$ 4,000,000
PECO Energy Co [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																							0
PECO Energy Co [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																0
PECO Energy Co [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0				0					0
PECO Energy Co [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0				0					0
PECO Energy Co [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		36,000,000				36,000,000					36,000,000
PECO Energy Co [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		1,000,000				1,000,000					1,000,000
PECO Energy Co [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		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
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[3]																																								10,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[3],[4],[8]																																								$ 26,000,000
Public Utilities, Approved Return on Equity, Percentage																																									10.50%
Proposed Capital Expenditure																																									$ 12,000,000
Regulatory Assets																																		571,000,000				571,000,000					571,000,000
Amortization Rate Stabilization Deferral																																									0		7,000,000		81,000,000
Estimated number of smart meters to be installed																																																		0
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					5,000,000
Regulatory Liability, Current																														77,000,000				62,000,000				62,000,000			77,000,000		62,000,000
Regulatory liabilities, noncurrent																														1,192,000,000				1,101,000,000				1,101,000,000			1,192,000,000		1,101,000,000
Revenues																														799,000,000	731,000,000	662,000,000	977,000,000	813,000,000	738,000,000	674,000,000	951,000,000				3,169,000,000		3,176,000,000		3,233,000,000
Business Combination, Integration Related Costs																																									1,000,000	[1],[6]	4,000,000	[1],[6]	(1,000,000)
Regulatory Liabilities																														1,269,000,000				1,163,000,000				1,163,000,000			1,269,000,000		1,163,000,000
Prior Year Revenue Adjustment	[3]																																								4,000,000
Accounts Payable, Current																														295,000,000				265,000,000				265,000,000			295,000,000		265,000,000
Payments to Acquire Property, Plant, and Equipment																																									959,000,000		882,000,000		934,000,000
Baltimore Gas and Electric Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																															$ 200,000,000
Proposed Capital Expenditure																																															$ 732,000,000
Baltimore Gas and Electric Company [Member] | Electric Distribution [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											$ 61,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 43,000,000
Tax Savings From Tax Cuts and Jobs Act																								$ 31,000,000
Baltimore Gas and Electric Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																									18,000,000
Baltimore Gas and Electric Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																51,000,000
Baltimore Gas and Electric Company [Member] | Difference between Carrying Value and Fair Value [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														133,000,000				139,000,000				139,000,000			133,000,000		139,000,000
Baltimore Gas and Electric Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Baltimore Gas and Electric Company [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Baltimore Gas and Electric Company [Member] | AMI programs - Deployment Costs
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																				52,000,000
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														48,000,000				53,000,000		56,000,000		53,000,000			48,000,000		53,000,000
Baltimore Gas and Electric Company [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		16,000,000				16,000,000					16,000,000
Baltimore Gas and Electric Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		6,000,000				6,000,000					6,000,000
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
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																																					444,000,000
Regulatory Assets																																		3,047,000,000				3,047,000,000					3,047,000,000
Amortization Rate Stabilization Deferral																																									14,000,000		(17,000,000)
Amount of Impairment to Carrying Amount of Regulatory Assets																																		27,000,000				27,000,000					27,000,000
Regulatory Liability, Current																														84,000,000				56,000,000				56,000,000			84,000,000		56,000,000
Regulatory liabilities, noncurrent																														1,864,000,000				1,872,000,000				1,872,000,000			1,864,000,000		1,872,000,000
Revenues																														1,117,000,000	1,361,000,000	1,076,000,000	1,251,000,000	1,121,000,000	1,310,000,000	1,074,000,000	1,175,000,000				4,805,000,000		4,679,000,000
Business Combination, Integration Related Costs																																									0	[1],[6]	(6,000,000)	[1],[6]	28,000,000
Regulatory Liabilities																														1,948,000,000				1,928,000,000				1,928,000,000			1,948,000,000		1,928,000,000
Impairment of Long-Lived Assets to be Disposed of																																				25,000,000
Accounts Payable, Current																														496,000,000				348,000,000				348,000,000			496,000,000		348,000,000
Payments to Acquire Property, Plant, and Equipment																																									1,375,000,000		1,396,000,000
Pepco Holdings LLC [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																84,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amortization Rate Stabilization Deferral																																								$ (5,000,000)
Revenues																																								3,643,000,000			4,679,000,000
Business Combination, Integration Related Costs	[6]																																							69,000,000	0		(18,000,000)	[1]
Payments to Acquire Property, Plant, and Equipment																																								$ 1,008,000,000
Pepco Holdings LLC [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														159,000,000				190,000,000				190,000,000			159,000,000		190,000,000
Pepco Holdings LLC [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														569,000,000				619,000,000				619,000,000			569,000,000		619,000,000
Pepco Holdings LLC [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														120,000,000				134,000,000				134,000,000			120,000,000		134,000,000
Pepco Holdings LLC [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														93,000,000				30,000,000				30,000,000			93,000,000		30,000,000
Pepco Holdings LLC [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														39,000,000				39,000,000				39,000,000			39,000,000		39,000,000
Pepco Holdings LLC [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														255,000,000				310,000,000				310,000,000			255,000,000		310,000,000
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																														320,000,000											320,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																									6,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																																								$ 8,000,000
Public Utilities, Approved Return on Equity, Percentage	[5]																																								10.50%
Projected Capital Expenditures																																			500,000,000
Regulatory Assets																																		891,000,000				891,000,000					891,000,000
Amortization Rate Stabilization Deferral																																									$ 14,000,000		(17,000,000)		(12,000,000)
Amount of Impairment to Carrying Amount of Regulatory Assets																																		14,000,000				14,000,000					14,000,000
Regulatory Liability, Current																														7,000,000				3,000,000				3,000,000			7,000,000		3,000,000
Regulatory liabilities, noncurrent																														822,000,000				829,000,000				829,000,000			822,000,000		829,000,000
Revenues																														531,000,000	628,000,000	523,000,000	557,000,000	510,000,000	604,000,000	514,000,000	530,000,000				2,239,000,000		2,158,000,000		2,186,000,000
Regulatory Liabilities																														829,000,000				832,000,000				832,000,000			829,000,000		832,000,000
Alternative Net Capital Requirement																																			250,000,000
Capital ProjectFundedByBonds																																			187,500,000						30,000,000							$ 127,000,000
CapitalProjectFundedByAgency																																			62,500,000
Prior Year Revenue Adjustment																																									2,000,000
Accounts Payable, Current																														214,000,000				139,000,000				139,000,000			214,000,000		139,000,000
Payments to Acquire Property, Plant, and Equipment																																									656,000,000		628,000,000		586,000,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 30,000,000																								$ 66,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount							$ 4,000,000					$ (15,000,000)		$ (24,000,000)				$ 3,000,000
Tax Savings From Tax Cuts and Jobs Act																							$ 39,000,000
Potomac Electric Power Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																									13,000,000
Potomac Electric Power Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																84,000,000
Potomac Electric Power Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														159,000,000				190,000,000				190,000,000			159,000,000		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				9,000,000			9,000,000		9,000,000
Potomac Electric Power Company [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														9,000,000				11,000,000				11,000,000			9,000,000		11,000,000
Potomac Electric Power Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														90,000,000				100,000,000				100,000,000			90,000,000		100,000,000
Potomac Electric Power Company [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														84,000,000				8,000,000				8,000,000			84,000,000		8,000,000
Potomac Electric Power Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														18,000,000				20,000,000				20,000,000			18,000,000		20,000,000
Potomac Electric Power Company [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														188,000,000				229,000,000				229,000,000			188,000,000		229,000,000
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 & Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																									14,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																																								$ 27,000,000
Public Utilities, Approved Return on Equity, Percentage	[5]																																								10.50%
Regulatory Assets																																		314,000,000				314,000,000					314,000,000
Amortization Rate Stabilization Deferral																																									$ 0		0		2,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets																																		6,000,000				6,000,000					6,000,000
Regulatory Liability, Current																														59,000,000				42,000,000				42,000,000			59,000,000		42,000,000
Regulatory liabilities, noncurrent																														606,000,000				593,000,000				593,000,000			606,000,000		593,000,000
Revenues																														331,000,000	328,000,000	289,000,000	384,000,000	330,000,000	327,000,000	282,000,000	362,000,000				1,332,000,000		1,300,000,000		1,277,000,000
Business Combination, Integration Related Costs																																									0	[1],[6]	(7,000,000)	[1],[6]	20,000,000
Regulatory Liabilities																														665,000,000				635,000,000				635,000,000			665,000,000		635,000,000
Prior Year Revenue Adjustment																																									13,000,000
Accounts Payable, Current																														111,000,000				82,000,000				82,000,000			111,000,000		82,000,000
Payments to Acquire Property, Plant, and Equipment																																									364,000,000		428,000,000		349,000,000
Delmarva Power & Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[7]									$ (7,000,000)
Public Utilities, Approved Rate Increase (Decrease), Amount																											$ 13,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																					$ 12,000,000	[7]						$ 19,000,000
Public Utilities, Approved Return on Equity, Percentage																											9.50%
Tax Savings From Tax Cuts and Jobs Act																					19,000,000
Delmarva Power & Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[7]						$ (4,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[7]																				4,000,000
Tax Savings From Tax Cuts and Jobs Act																					$ 7,000,000
Delmarva Power & Light Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																									12,000,000
Delmarva Power & Light Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																0
Delmarva Power & Light Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Delmarva Power & Light Company [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Delmarva Power & Light Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														30,000,000				34,000,000				34,000,000			30,000,000		34,000,000
Delmarva Power & Light Company [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				7,000,000				7,000,000			0		7,000,000
Delmarva Power & Light Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														11,000,000				10,000,000				10,000,000			11,000,000		10,000,000
Delmarva Power & Light Company [Member] | Energy efficiency and demand response programs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														67,000,000				81,000,000				81,000,000			67,000,000		81,000,000
Delmarva Power & Light Company [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																														89,000,000											89,000,000
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount								$ 40,000,000																																	4,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																																								$ 0
Public Utilities, Approved Return on Equity, Percentage	[5]																																								10.50%
Regulatory Assets																																		430,000,000				430,000,000					430,000,000
Amortization Rate Stabilization Deferral																																									$ 0		0		0
Amount of Impairment to Carrying Amount of Regulatory Assets																																		7,000,000				7,000,000					7,000,000
Regulatory Liability, Current																														18,000,000				11,000,000				11,000,000			18,000,000		11,000,000
Regulatory liabilities, noncurrent																														402,000,000				411,000,000				411,000,000			402,000,000		411,000,000
Revenues																														254,000,000	406,000,000	265,000,000	$ 310,000,000	271,000,000	$ 370,000,000	$ 270,000,000	$ 275,000,000				1,236,000,000		1,186,000,000		1,257,000,000
Business Combination, Integration Related Costs																																									0	[1],[6]	(6,000,000)	[1],[6]	19,000,000
Regulatory Liabilities																														420,000,000				422,000,000				422,000,000			420,000,000		422,000,000
Prior Year Revenue Adjustment																																									(4,000,000)
Tax Savings From Tax Cuts and Jobs Act																				$ 23,000,000
Accounts Payable, Current																														154,000,000				118,000,000				118,000,000			154,000,000		118,000,000
Payments to Acquire Property, Plant, and Equipment																																									335,000,000		312,000,000		$ 311,000,000
Atlantic City Electric Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Payments to Acquire Property, Plant, and Equipment																																														$ 338,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[9]					$ 122,000,000
Atlantic City Electric Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																									11,000,000
Atlantic City Electric Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Accounts Payable, Current																																$ 0
Atlantic City Electric Company [Member] | DC PLUG charge
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Atlantic City Electric Company [Member] | Fair value of long-term debt
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Atlantic City Electric Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														0				0				0			0		0
Atlantic City Electric Company [Member] | Electric Energy and Natural Gas Costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														9,000,000				15,000,000				15,000,000			9,000,000		15,000,000
Atlantic City Electric Company [Member] | Merger integration costs
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																														10,000,000				9,000,000				9,000,000			10,000,000		9,000,000
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
One-Time Revenue Adjustment [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																															76,000,000								76,000,000
One-Time Revenue Adjustment [Member] | Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																															51,000,000								51,000,000
One-Time Revenue Adjustment [Member] | Baltimore Gas and Electric Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																															15,000,000								15,000,000
One-Time Revenue Adjustment [Member] | Pepco Holdings LLC [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																															10,000,000								10,000,000
One-Time Revenue Adjustment [Member] | Potomac Electric Power 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
One-Time Revenue Adjustment [Member] | Delmarva Power & Light Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																															5,000,000								5,000,000
One-Time Revenue Adjustment [Member] | Atlantic City Electric Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																															$ 2,000,000								$ 2,000,000

[1] 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.

[2] Does not include an offsetting receivable from New Jersey Utilities of $16 million as of December 31, 2018.

[3] The time period for any formal challenges to the annual transmission formula rate update filings expired with no formal challenges submitted.

[4] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVlYzRiNDIxOTkxNDRkN2ViNWYzYTRhOTVmMjFkNDYzfFRleHRTZWxlY3Rpb246MzY0MUFFQzNGNTE3Mzk3OTI2RjIxNTRFRUQyNkYyMzMM}

[5] As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50%, 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.

[6] (b)For the year ended December 31, 2017, includes deferrals of previously incurred integration costs as regulatory assets of $24 million, $8 million, $8 million, and $8 million at PHI, Pepco, DPL and ACE, respectively. For the year ended December 31, 2016, includes deferrals of previously incurred integration costs as regulatory assets of $8 million, $6 million, $11 million and $4 million at ComEd, BGE, Pepco and DPL, respectively. For the Successor period March 24, 2016 to December 31, 2016, includes deferrals of previously incurred integration costs as regulatory assets of $16 million at PHI. See Note 4 - Regulatory Matters for additional information.

[7] Includes the annual ongoing TCJA tax savings further discussed below.

[8] BGE's transmission revenue requirement includes a FERC approved dedicated facilities charge of $12 million to recover the costs of providing transmission service to specifically designated load by BGE.

[9] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVlYzRiNDIxOTkxNDRkN2ViNWYzYTRhOTVmMjFkNDYzfFRleHRTZWxlY3Rpb246NUYyM0EwMDI1MDhGQUUyMUZEMzExNTNGOUY0NjExNDUM}