Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 637	$ 602
Noncurrent		4,302	4,187
Regulatory Liabilities		4,939	4,789
Regulatory Assets		11,381	11,388
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		66	76
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		48	47
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,776	2,607
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,598	1,601
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		39	39
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		185	185
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8	8
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18	20
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		133	134
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		65	72
Rate Stabilization Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		67	50
Noncurrent		94	110
Regulatory Liabilities		161	160
Regulatory Assets		690	712
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] | Abandonment costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Gas Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets			1
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
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		136	141
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] | 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	[1]	2	0
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		20	19
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	3
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		82	79
Noncurrent		154	158
Regulatory Liabilities		236	237
Regulatory Assets		3,444	3,504
Pepco Holdings LLC [Member] | Electric Transmission And Distribution Tax Repairs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Nuclear Decommissioning [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Removal Costs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		134	136
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	39	39
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	3
Pepco Holdings LLC [Member] | Dlc Program Cost [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Gas Distribution Tax Repairs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Over Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		27	18
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		34	41
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		161	127
Noncurrent		530	517
Regulatory Liabilities		691	644
Regulatory Assets		1,748	1,710
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10
PECO Energy Co [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	4
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		66	76
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		482	438
PECO Energy Co [Member] | Removal Costs [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		44	41
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8	8
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18	20
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		66	56
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7	5
PECO Energy Co [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13	8
PECO Energy Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			10
PECO Energy Co [Member] | Default Service Provider Program [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		41	34
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		311	329
Noncurrent		3,492	3,369
Regulatory Liabilities		3,803	3,698
Regulatory Assets		1,215	1,167
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,294	2,169
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,328	1,324
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		139	141
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			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	[3]	38	60
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4	4
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		32	30
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6	30
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		10	11
Noncurrent		19	20
Regulatory Liabilities		29	31
Regulatory Assets		852	852
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	5
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] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
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		17	18
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	3
Potomac Electric Power Company [Member] | Dlc Program Cost [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	8
Potomac Electric Power Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3	2
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5	3
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		47	43
Noncurrent		95	97
Regulatory Liabilities		142	140
Regulatory Assets		367	348
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1	3
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] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
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		117	118
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] | 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]	12	5
Delmarva Power and Light Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13	17
Delmarva Power and Light Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2
Delmarva Power and Light Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9	2
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		25	25
Noncurrent		0	0
Regulatory Liabilities		25	25
Regulatory Assets		501	501
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	4
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] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
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] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Atlantic City Electric Company [Member] | Dlc Program Cost [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	[6]	8	5
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		17	20
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6	1
Under-Recovered Electric Revenue Decoupling [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		25
Under Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		71	89
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[1]	19	38
Under Recovered Energy And Transmission Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		34	28
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		0	0
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[3]	18	23
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		6	6
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[5]	5	5
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[6]	23	17
UnderRecoveredNaturalGasDecouplingRevenue [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		$ 6	$ 2

[1] As of March 31, 2017, PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246NThDMDVEQzYxNzNFNTQ4RUJFNEFCOUVFNjQ1RDA3RDIM}

[3] As of March 31, 2017, ComEd’s regulatory asset of $18 million included $10 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 March 31, 2017, ComEd’s regulatory liability of $38 million included $6 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.

[4] As of March 31, 2017, BGE's regulatory asset of $19 million included $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $13 million related to under-recovered electric energy costs, and $3 million of abandonment costs to be recovered upon FERC approval. As of March 31, 2017, BGE's regulatory liability consisted of $2 million related to over-recovered natural gas costs. 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.

[5] As of March 31, 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 March 31, 2017, Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of 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.

[6] As of March 31, 2017, DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017, DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission 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.