Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 10,246		$ 10,388
Regulatory Liability, Current		522		523
Regulatory Liability, Noncurrent		9,724		9,865
Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		26		30
Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	5,189		5,241
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,969		3,064
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,570		1,573
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		35		36
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		16		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		27		35
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		9
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2],[4],[5],[6]	153	[3],[7]	111
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	14
Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		81		63
Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		112
Over Recovered Uncollectible Accounts Expense [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4		2
Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	1
TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	54
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		84		82
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6,424		6,577
Regulatory Liability, Current		212		249
Regulatory Liability, Noncurrent		6,212		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]	2,458		2,479
Commonwealth Edison Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,464		2,528
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,348		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		4		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	[4]	53		47
Commonwealth Edison Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		81		63
Commonwealth Edison Co [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		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		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		8		6
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		479		484
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		21		14
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		32		33
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		646		690
Regulatory Liability, Current		117		141
Regulatory Liability, Noncurrent		529		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
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		505		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		11		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		27		35
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		9
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[6]	56		60
PECO Energy Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		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		0
PECO Energy Co [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	10
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		22		24
PECO Energy Co [Member] | Default Service Provider Program [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		44		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		9		12
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,185		1,163
Regulatory Liability, Current		102		62
Regulatory Liability, Noncurrent		1,083		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]	1,011		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		92		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		22	[3]	0
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[8]	11
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		0
Baltimore Gas and Electric Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	17
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		32		26
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		135		137
Pepco Holdings LLC [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,965		1,928
Regulatory Liability, Current		77		56
Regulatory Liability, Noncurrent		1,888		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]	1,720		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		130		130
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		35		36
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1		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],[5]	22	[7]	4
Pepco Holdings LLC [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
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		4		2
Pepco Holdings LLC [Member] | Merger Integration Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[9]	1
Pepco Holdings LLC [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	27
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		22		26
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		845		832
Regulatory Liability, Current		7		3
Regulatory Liability, Noncurrent		838		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]	804		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		4	[7]	0
Potomac Electric Power Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		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		0
Potomac Electric Power Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	14
Potomac Electric Power Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3		3
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		146		147
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		646		635
Regulatory Liability, Current		48		42
Regulatory Liability, Noncurrent		598		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]	506		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		110		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	[5]	6		1
Delmarva Power and Light Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
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		1
Delmarva Power and Light Company [Member] | TCJA income tax benefit over-recoveries [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[10]	7
Delmarva Power and Light Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13		14
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		147		148
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		437		422
Regulatory Liability, Current		21		11
Regulatory Liability, Noncurrent		416		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]	410		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		1		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]	12		3
Atlantic City Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		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		4		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]	6
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4		6
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		147		$ 147
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 12

[1] As of March 31, 2018, includes transmission-related income tax regulatory liabilities that require FERC approval separate from the transmission formula rate of $479 million, $135 million, $146 million, $147 million and $147 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 March 31, 2018, ACE's regulatory asset of $24 million included $9 million of transmission costs recoverable through its FERC approved formula rate and $15 million of under-recovered electric energy costs. As of March 31, 2018, ACE's regulatory liability of $12 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 March 31, 2018, BGE's regulatory asset of $21 million included $13 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $5 million related to under-recovered electric energy costs and $3 million of abandonment costs to be recovered upon FERC approval. As of March 31, 2018, BGE's regulatory liability of $22 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 March 31, 2018, ComEd’s regulatory asset of $8 million represents transmission costs recoverable through its FERC approved formula rate. As of March 31, 2018, ComEd’s regulatory liability of $53 million included $21 million related to over-recovered energy costs and $32 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 March 31, 2018, DPL's regulatory asset of $14 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $3 million related to under-recovered electric energy costs. As of March 31, 2018, DPL's regulatory liability of $6 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 March 31, 2018, PECO's regulatory liability of $56 million included $44 million related to over-recovered costs under the DSP program, $3 million related to the over-recovered transmission service charges and $9 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.

[7] As of March 31, 2018, Pepco's regulatory asset of $7 million included $4 million of transmission costs recoverable through its FERC approved formula rate and $3 million related to under-recovered electric energy costs. As of March 31, 2018, Pepco's regulatory liability of $4 million related to over-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.

[8] Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of March 31, 2018, BGE had a regulatory asset of $6 million related to under-recovered electric revenue decoupling and a regulatory liability of $11 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 March 31, 2018, DPL’s regulatory asset of $11 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 $2 million authorized for recovery in Delaware gas rates.

[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 further details on the regulatory proceedings.