Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		3 Months Ended					6 Months Ended			12 Months Ended
		Jun. 30, 2017		Jun. 30, 2016	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016	Dec. 31, 2016
Regulatory Assets [Line Items]
Current		$ 1,293					$ 1,293			$ 1,342
Noncurrent		9,945					9,945			10,046
Regulatory Assets		11,238					11,238			11,388
Business Combination, Integration Related Costs	[1],[2]	8		$ 1			17		$ 103
Renewable Portfolio Standard [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	4,086					4,086			4,162
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	2,091					2,091			2,016
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		679					679			701
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		239					239			188
Energy Efficiency Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		117					117			124
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		782					782			812
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		918					918			1,085
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3			5
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		119					119			111
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		289					289			305
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			56
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		258					258			260
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		69					69			89
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			36
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5					5			10
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										7
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		590					590			621
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32					32			25
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		74					74			27
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			8
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			34
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		47					47			31
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108					108			138
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			11
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		500					500			477
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	1,025					1,025
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			49
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current		182					182			190
Noncurrent		1,050					1,050			977
Regulatory Assets		1,232					1,232			1,167
Business Combination, Integration Related Costs	[2],[5]	0		1			1		(7)
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	76					76			75
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		163					163			164
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[6]	239					239			188
Commonwealth Edison Co [Member] | Energy Efficiency Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39					39			42
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		84					84			76
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		266					266			278
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			56
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		256					256			258
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[7]	8					8			23
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member] | Pepco Holdings [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9					9			11
Business Combination, Integration Related Costs										8
Commonwealth Edison Co [Member] | 561710 Exterminating and Pest Control Services [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Commonwealth Edison Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			7
Business Combination, Integration Related Costs									8
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22					22			22
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			54
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		29					29			23
Commonwealth Edison Co [Member] | Annual Reconciliations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		184					184			134
Commonwealth Edison Co [Member] | ElectricTransmissionCostsUnderRecovery [Member]
Regulatory Assets [Line Items]
Regulatory Assets										15
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14					14			20
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current		46					46			29
Noncurrent		1,732					1,732			1,681
Regulatory Assets		1,778					1,778			1,710
Business Combination, Integration Related Costs	[2]	1		1			2		2
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,645					1,645			1,583
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		43					43			49
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1					1			1
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23					23			23
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23					23			26
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1					1			0
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1					1			1
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
PECO Energy Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22					22			7
PECO Energy Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			11
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9					9			9
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current		197					197			208
Noncurrent		495					495			504
Regulatory Assets		692					692			712
Business Combination, Integration Related Costs	[2],[8]	1		(5)			2		(4)
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32					32
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	100					100			98
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Noncurrent		225					225			230
Regulatory Assets		225					225			230
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7					7			7
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3			5
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		12					12			12
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[9]	21					21			38
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			1
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5					5			10
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										7
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		271					271			285
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	7					7			10
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member] | Pepco Holdings [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]									6
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[12]	35					35			3
Baltimore Gas and Electric Company [Member] | UnderRecoveredNaturalGasDecouplingRevenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11					11			2
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets										3
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24					24			1
Baltimore Gas and Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			5
Business Combination, Integration Related Costs									6
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		41					41			38
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		137					137
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4			4
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2					2			3
Baltimore Gas and Electric Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			28
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs	[2],[13]					$ 29	(2)
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current		605					605			653
Noncurrent		2,715					2,715			2,851
Regulatory Assets		3,320					3,320			3,504
Business Combination, Integration Related Costs	[2],[13]	2		(1)	$ 55
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Deferred Income Tax Charge [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	270					270			260
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		248					248			258
Pepco Holdings LLC [Member] | Under Recovered Distribution Service Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Loss on Reacquired Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		77					77			81
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		645					645			671
Pepco Holdings LLC [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		918					918			1,085
Pepco Holdings LLC [Member] | Employee Severance [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Asset Retirement Obligation Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Environmental Restoration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Renewable Energy And Associated REC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2					2			2
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39					39			28
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			35
Pepco Holdings LLC [Member] | Electric Generation Related Regulatory Asset [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Rate Stabilization Deferral [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Pepco Holdings LLC [Member] | Energy Efficiency And Demand Response Programs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		318					318			335
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25					25			15
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39					39			24
Pepco Holdings LLC [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6
Pepco Holdings LLC [Member] | Deferred Project Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets										8
Pepco Holdings LLC [Member] | Workers Compensation and Long-Term Disability [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			34
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25					25			24
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108					108			138
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		500					500			477
Pepco Holdings LLC [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs							8		12
Pepco Holdings LLC [Member] | Regulatory Assets [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32					32			29
Potomac Electric Power Company [Member]
Regulatory Assets [Line Items]
Current		165					165			162
Noncurrent		682					682			690
Regulatory Assets		847					847			852
Business Combination, Integration Related Costs	[2],[14]	1		(4)			2		23
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	176					176			171
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		167					167			174
Potomac Electric Power Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		16					16			17
Potomac Electric Power Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Potomac Electric Power Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[15]	6					6			6
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			12
Potomac Electric Power Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Potomac Electric Power Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		236					236			250
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		12		9	9		12		9	11	[16]
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		31					31			21
Potomac Electric Power Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			34
Potomac Electric Power Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		138					138			134
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		21					21			22
Business Combination, Integration Related Costs									9
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		33					33			31
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2					2
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4
Delmarva Power and Light Company [Member]
Regulatory Assets [Line Items]
Current		71					71			59
Noncurrent		299					299			289
Regulatory Assets		370					370			348
Business Combination, Integration Related Costs	[2],[17]	0		0			(7)		16
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	41					41			38
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		81					81			84
Delmarva Power and Light Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			9
Delmarva Power and Light Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Delmarva Power and Light Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1					1			0
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[18]	6					6			5
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			5
Delmarva Power and Light Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Delmarva Power and Light Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		82					82			85
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13		3	$ 3		13		3
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			3
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			8
Delmarva Power and Light Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		15					15			14
Delmarva Power and Light Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		95					95			88
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			5
Business Combination, Integration Related Costs							8		3
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22					22			20
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4			4	[16]
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets										1
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			4
Atlantic City Electric Company [Member]
Regulatory Assets [Line Items]
Current		89					89			96
Noncurrent		406					406			405
Regulatory Assets		495					495			501
Business Combination, Integration Related Costs	[2]	1		$ 2			2		$ 15
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	53					53			51
Atlantic City Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			6
Atlantic City Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1					1			2
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]	27	[18]				27	[18]		17
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		18					18			18
Atlantic City Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0
Atlantic City Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			10
Atlantic City Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108					108			138
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		268					268			255
Atlantic City Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4			4
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		20					20			19
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11					11			6
Atlantic City Electric Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 16					$ 16			$ 11

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

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

[3] As of June 30, 2017 and December 31, 2016, the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,025 million and $995 million, respectively, as a result of the PHI Merger related to unrecognized costs that are probable of regulatory recovery. The regulatory assets are amortized over periods from 3 to 15 years, depending on the underlying component. Pepco, DPL and ACE are currently recovering these costs through base rates. Pepco, DPL and ACE are not earning a return on the recovery of these costs in base rates.

[4] As of June 30, 2017, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $41 million, $33 million, $22 million and $20 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2016, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $38 million, $31 million, $20 million and $19 million for ComEd, BGE, Pepco, DPL and ACE, respectively.

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

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

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

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

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

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

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

[12] Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of June 30, 2017, BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $11 million related to under-recovered natural gas revenue decoupling. As of December 31, 2016, BGE had a regulatory asset of $2 million related to under-recovered natural gas revenue decoupling and $1 million related to under-recovered electric revenue decoupling.

[13] (g)For the six months ended June 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three months ended June 30, 2016 and the Successor period March 24, 2016 to June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $12 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

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

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

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

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

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