Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Major Customer [Line Items]
Revenue from Related Parties	$ 0	$ 0	$ 0	$ 0
Revenues	8,929	9,403	26,096	27,170
Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues	8,929	9,403	26,096	27,170
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4	4	13	23
Revenues	1,583	1,598	4,342	4,508
Commonwealth Edison Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(56)	(15)	(98)	(27)
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,633	1,606	4,418	4,512
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(50)	(8)	(76)	(4)
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	2	4	5
Revenues	778	757	2,333	2,275
PECO Energy Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(11)	1	(16)	2
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	2	4	5
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	0	0	0	0
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	785	753	2,338	2,263
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(7)	4	(5)	12
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	6	6	18	18
Revenues	703	731	2,327	2,369
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(5)	(6)	11	(23)
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	2	1	5	5
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4	5	13	0
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	704	732	2,303	2,379
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(1)	(1)	24	(10)
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4	3	11	11
Revenues	1,380	1,361	3,700	3,688
Pepco Holdings LLC [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(9)	(5)	4	7
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties		3
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,386	1,363	3,689	3,673
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(6)	(2)	11	15
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	2	2	5	5
Revenues	642	628	1,748	1,708
Potomac Electric Power Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(3)	(4)	10	6
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	643	630	1,732	1,697
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(1)	(2)	16	11
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	2	5	6
Revenues	319	328	987	1,001
Delmarva Power and Light Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(6)	0	(6)	5
Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	325	327	991	993
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(6)	1	(4)	8
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	1	2	2
Revenues	419	406	966	981
Atlantic City Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	(1)	0	(4)
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	418	407	966	985
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	1	(1)	0	(4)
Electricity, US Regulated | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,268	4,270	11,609	11,766
Electricity, US Regulated | Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,635	1,609	4,427	4,512
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,633	1,606	4,418	4,512
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6	7	22	23
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	865	861	2,221	2,277
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	393	391	1,103	1,132
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	141	131	399	411
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12	11	35	36
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	222	212	660	656
Electricity, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	726	697	1,914	1,886
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	723	696	1,907	1,881
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	10	10
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	479	458	1,231	1,199
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	109	108	304	306
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	63	64	163	174
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	7	23	21
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	63	59	186	181
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	623	652	1,814	1,847
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	621	649	1,809	1,842
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	4	10	10
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	352	366	1,019	1,054
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	64	68	193	196
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	116	117	335	325
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7	7	20	21
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	82	91	242	246
Electricity, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,365	1,340	3,570	3,541
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,366	1,339	3,574	3,544
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	7	8
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	741	726	1,816	1,839
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	147	140	387	370
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	297	303	843	845
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	17	14	47	44
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	164	156	481	446
Electricity, US Regulated | Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	643	630	1,733	1,697
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	643	630	1,732	1,697
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	2	6	5
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	311	306	792	792
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	41	39	114	104
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	222	230	633	632
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11	8	27	24
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	58	47	166	145
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	304	302	872	861
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	305	303	876	864
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	1	1	3
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	178	180	499	513
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	48	48	141	138
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26	25	75	74
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	50	47	151	129
Electricity, US Regulated | Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	417	406	964	983
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	418	407	966	985
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	252	240	525	534
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	58	53	132	128
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	49	48	135	139
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	56	63	164	174
Natural Gas, US Regulated | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	163	162	1,046	1,017
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62	57	431	382
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62	57	431	382
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	1	0
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	38	36	285	259
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	17	15	122	102
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	1	1
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	5	18	16
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	1	5	4
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	79	79	484	527
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	83	83	494	537
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	1	3	3
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	49	46	327	345
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	8	55	55
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	17	93	88
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	12	19	49
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	23	115	129
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	24	115	129
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	8	64	68
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	5	30	31
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	2	4	7
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	11	12
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	6	6	11
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	24	116	129
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	24	115	129
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	1	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	8	64	68
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	5	30	31
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	2	4	7
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	11	12
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	6	6	11
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 0	$ 0	$ 0	$ 0