Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		Sep. 30, 2018		Jun. 30, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 10,445			$ 10,388
Regulatory Liability, Current		689			523
Regulatory Liability, Noncurrent		9,756			9,865
Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		20			30
Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	5,054			5,241
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,958			3,064
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,566			1,573
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		34			36
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10			23
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7			7
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10			35
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4			9
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	372	[3],[6]		111	[7]
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	21
Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		140			63
Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18			112
Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2			2
Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	3
TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	108
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		118			82
PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				$ 221
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6,638			6,577
Regulatory Liability, Current		320			249
Regulatory Liability, Noncurrent		6,318			6,328
Commonwealth Edison Co [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	2,418			2,479
Commonwealth Edison Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,469			2,528
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,370			1,338
Commonwealth Edison Co [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3			4
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Commonwealth Edison Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	204	[3],[6]		47	[7]
Commonwealth Edison Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	0
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		140			63
Commonwealth Edison Co [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18			112
Commonwealth Edison Co [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	0
Commonwealth Edison Co [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	0
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		16			6
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		464			484
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		72			14
Commonwealth Edison Co [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		101		122
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		31			33
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		740			690
Regulatory Liability, Current		159			141
Regulatory Liability, Noncurrent		581			549
PECO Energy Co [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0	[1]
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		489			536
PECO Energy Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
PECO Energy Co [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5			19
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7			7
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10			35
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4			9
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	143	[3],[6]		60	[7]
PECO Energy Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	0
PECO Energy Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
PECO Energy Co [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
PECO Energy Co [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	0
PECO Energy Co [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	61
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		21			24
PECO Energy Co [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		85		85
PECO Energy Co [Member] | Default Service Provider Program [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		43			36
PECO Energy Co [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3			12
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		12			12
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,165			1,163
Regulatory Liability, Current		95			62
Regulatory Liability, Noncurrent		1,070			1,101
Baltimore Gas and Electric Company [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	1,015			1,032
Baltimore Gas and Electric Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		67			105
Baltimore Gas and Electric Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	7	[3],[6]		0	[7]
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	17
Baltimore Gas and Electric Company [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	0
Baltimore Gas and Electric Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	19
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		40			26
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		135			137
Baltimore Gas and Electric Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				0
Pepco Holdings LLC [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,882			1,928
Regulatory Liability, Current		99			56
Regulatory Liability, Noncurrent		1,783			1,872
Pepco Holdings LLC [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	1,621			1,730
Pepco Holdings LLC [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		129			130
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		34			36
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2			0
Pepco Holdings LLC [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	18	[3],[6]		4	[7]
Pepco Holdings LLC [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	4
Pepco Holdings LLC [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Pepco Holdings LLC [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2			2
Pepco Holdings LLC [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	3
Pepco Holdings LLC [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	28
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		41			26
Pepco Holdings LLC [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				14
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		764			832
Regulatory Liability, Current		5			3
Regulatory Liability, Noncurrent		759			829
Potomac Electric Power Company [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	734			809
Potomac Electric Power Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		20			20
Potomac Electric Power Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	0	[3],[6]		0	[7]
Potomac Electric Power Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	0
Potomac Electric Power Company [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	0
Potomac Electric Power Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	6
Potomac Electric Power Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4			3
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		136			147
Potomac Electric Power Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				0
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		654			635
Regulatory Liability, Current		67			42
Regulatory Liability, Noncurrent		587			593
Delmarva Power and Light Company [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	493			510
Delmarva Power and Light Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		109			110
Delmarva Power and Light Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	14	[3],[6]		1	[7]
Delmarva Power and Light Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	4
Delmarva Power and Light Company [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	3
Delmarva Power and Light Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	8
Delmarva Power and Light Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		23			14
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		145			148
Delmarva Power and Light Company [Member] | Over Recovered Electric Energy and Gas Fuel Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[5]	4
Delmarva Power and Light Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10	[5]	10
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		428			422
Regulatory Liability, Current		27			11
Regulatory Liability, Noncurrent		401			411
Atlantic City Electric Company [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	394			411
Atlantic City Electric Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2			0
Atlantic City Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5]	4	[3],[6]		3	[7]
Atlantic City Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	0
Atlantic City Electric Company [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0			0
Atlantic City Electric Company [Member] | Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2			2
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	0
Atlantic City Electric Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	14
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		12			6
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		141			$ 147
Atlantic City Electric Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3	[5]	$ 4
Atlantic City Electric Company [Member] | Over Recovered Electric Energy Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	$ 1

[1] As of September 30, 2018, includes transmission-related income tax regulatory liabilities that require FERC approval separate from the transmission formula rate of $464 million, $135 million, $136 million, $145 million and $141 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2017, includes transmission-related income tax regulatory liabilities that require FERC approval separate from the transmission formula rate of $484 million, $137 million, $147 million, $148 million and $147 million for ComEd, BGE, Pepco, DPL and ACE, respectively.

[2] As of September 30, 2018, ACE's regulatory asset of $14 million included $7 million of transmission costs recoverable through its FERC approved formula rate and $7 million of under-recovered electric energy costs. As of September 30, 2018, ACE's regulatory liability of $4 million included $3 million related to the PJM Transmission Rate Design Settlement and $1 million related to over-recovered electric energy costs. As of December 31, 2017, ACE's regulatory asset of $26 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $15 million of under-recovered electric energy costs. As of December 31, 2017, ACE's regulatory liability of $3 million related to over-recovered electric energy costs.

[3] As of September 30, 2018, BGE's regulatory asset of $72 million included $48 million related to the PJM Transmission Rate Design Settlement, $14 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $7 million related to under-recovered electric energy costs and $3 million of abandonment costs to be recovered upon FERC approval. As of September 30, 2018, BGE's regulatory liability of $7 million related to over-recovered natural gas costs. As of December 31, 2017, BGE’s regulatory asset of $23 million included $7 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $5 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval and $8 million of under-recovered natural gas costs.

[4] As of September 30, 2018, ComEd’s regulatory asset of $7 million represents transmission costs recoverable through its FERC approved formula rate. As of September 30, 2018, ComEd’s regulatory liability of $204 million included $101 million related to the PJM Transmission Rate Design Settlement, $72 million related to over-recovered energy costs and $31 million associated with revenues received for renewable energy requirements. As of December 31, 2017, ComEd’s regulatory asset of $6 million represents transmission costs recoverable through its FERC approved formula rate. As of December 31, 2017, ComEd’s regulatory liability of $47 million included $14 million related to over-recovered energy costs and $33 million associated with revenues received for renewable energy requirements.

[5] As of September 30, 2018, DPL's regulatory asset of $15 million included $14 million of transmission costs recoverable through its FERC approved formula rate and $1 million related to under-recovered electric energy costs. As of September 30, 2018, DPL's regulatory liability of $14 million included $10 million related to the PJM Transmission Rate Design Settlement and $4 million related to over-recovered electric energy and gas fuel costs. As of December 31, 2017, DPL's regulatory asset of $15 million included $8 million of transmission costs recoverable through its FERC approved formula rate and $7 million related to under-recovered electric energy costs. As of December 31, 2017, DPL's regulatory liability of $1 million related to over-recovered electric energy costs.

[6] As of September 30, 2018, Pepco's regulatory asset of $93 million included $74 million related to the PJM Transmission Rate Design Settlement, $7 million of transmission costs recoverable through its FERC approved formula rate and $12 million related to under-recovered electric energy costs. As of December 31, 2017, Pepco's regulatory asset of $11 million included $3 million of transmission costs recoverable through its FERC approved formula rate and $8 million of under-recovered electric energy costs.

[7] As of September 30, 2018, PECO’s regulatory asset of $50 million represents the under-recovered natural gas costs under the PGC. As of December 31, 2017, PECO’s regulatory asset of $1 million is related to under-recovered costs under the TSC program. As of September 30, 2018, PECO's regulatory liability of $143 million included $85 million related to the PJM Transmission Rate Design Settlement, $43 million related to over-recovered costs under the DSP program, $3 million related to the over-recovered transmission service charges and $12 million related to over-recovered non-bypassable transmission service charges. As of December 31, 2017, PECO's regulatory liability of $60 million included $36 million related to over-recovered costs under the DSP program, $12 million related to over-recovered non-bypassable transmission service charges and $12 million related to the over-recovered natural gas costs under the PGC.

[8] Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2018, BGE had a regulatory asset of less than $1 million related to under-recovered electric revenue decoupling and a regulatory liability of $17 million related to over-recovered natural gas revenue decoupling. As of December 31, 2017, BGE had a regulatory asset of $10 million related to under-recovered electric revenue decoupling and $4 million related to under-recovered natural gas revenue decoupling.

[9] As of September 30, 2018, DPL’s regulatory asset of $12 million represents previously incurred PHI integration costs, including $4 million authorized for recovery in Maryland, $5 million authorized for recovery in Delaware electric rates, $2 million authorized for recovery in Delaware gas rates and $1 million expected to be recovered in electric rates in the Delaware and Maryland service territories. As of September 30, 2018, DPL’s regulatory liability of $3 million represents net synergy savings incurred related to PHI integration costs that are expected to be returned in electric and gas rates in the Delaware service territory. As of December 31, 2017, DPL’s regulatory asset of $10 million represents previously incurred PHI integration costs, including $4 million authorized for recovery in Maryland, $5 million authorized for recovery in Delaware electric rates, and $1 million expected to be recovered in electric and gas rates in the Maryland and Delaware service territories.

[10] Represents over-recoveries related to the change in the federal income tax rate with the enactment of the TCJA. These regulatory liabilities will be amortized as the TCJA income tax benefits are passed back to customers. See Tax Cuts and Jobs Act disclosures above for additional information on the regulatory proceedings.