Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Major Customer [Line Items]
Revenues	$ 8,343	$ 8,929	$ 7,689	$ 9,477	$ 8,812	$ 9,401	$ 8,074	$ 9,691	$ 34,438	$ 35,978	$ 33,558
Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues									34,438	35,978	33,560
Operating Segments [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues									4,806	4,798	4,672
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenues	1,405	1,583	1,351	1,408	1,373	1,598	1,398	1,512	5,747	5,882	5,536
Revenue from Related Parties									30	27	15
Commonwealth Edison Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									(133)	(29)	43
Revenues											0
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									5,854	5,881	5,463
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									(107)	1	73
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenues	766	778	655	900	765	757	653	866	3,100	3,038	2,870
Revenue from Related Parties									6	8	7
PECO Energy Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									(21)	(7)	0
Revenues											0
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties									5	7	6
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									3,107	3,032	2,857
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									(7)	6	13
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties									1	1	1
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	779	703	649	976	799	731	662	977	3,106	3,169	3,176
Revenue from Related Parties									26	29	16
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									12	(26)	124
Revenues											0
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties									8	8	5
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									3,078	3,178	3,035
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									28	(9)	141
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties									18	21	11
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues	1,107	1,380	1,091	1,228	1,115	1,359	1,074	1,249	4,806	4,798	4,672
Revenue from Related Parties									14	15	50
Pepco Holdings LLC [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									(14)	(7)	33
Revenues											47
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties										15	3
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									4,810	4,794	4,583
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									(4)	4	89
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties										47
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenues	513	642	531	575	529	626	521	555	2,260	2,232	2,151
Revenue from Related Parties									5	6	6
Potomac Electric Power Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									(3)	(7)	19
Revenues											0
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									2,255	2,232	2,127
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									5	0	24
Delmarva Power & Light Company [Member]
Revenue, Major Customer [Line Items]
Revenues	319	319	287	380	331	328	289	384	1,306	1,332	1,300
Revenue from Related Parties									7	8	8
Delmarva Power & Light Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									(11)	4	6
Revenues											0
Delmarva Power & Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									1,315	1,324	1,290
Delmarva Power & Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									(9)	8	10
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	$ 274	$ 419	$ 274	$ 273	$ 254	$ 406	$ 265	$ 310	1,240	1,236	1,186
Revenue from Related Parties									3	3	2
Atlantic City Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									0	(4)	8
Revenues											0
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues									1,240	1,240	1,178
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues									0	(4)	8
Electricity, US Regulated [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									15,195	15,337	14,833
Electricity, US Regulated [Member] | Operating Segments [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									4,626	4,602	4,462
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									5,850	5,884	5,478
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									5,854	5,881	5,463
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,916	2,942	2,715
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,463	1,487	1,363
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									540	538	455
Electricity, US Regulated [Member] | 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									47	47	44
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									888	867	886
Electricity, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									26	30	30
Electricity, US Regulated [Member] | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,505	2,469	2,369
Electricity, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,497	2,464	2,363
Electricity, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,596	1,566	1,505
Electricity, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									404	404	401
Electricity, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									219	223	223
Electricity, US Regulated [Member] | 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									29	28	30
Electricity, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									249	243	204
Electricity, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									13	12	12
Electricity, US Regulated [Member] | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,368	2,428	2,384
Electricity, US Regulated [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,364	2,423	2,376
Electricity, US Regulated [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,326	1,382	1,365
Electricity, US Regulated [Member] | 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									254	257	254
Electricity, US Regulated [Member] | 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									436	429	427
Electricity, US Regulated [Member] | 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									27	28	31
Electricity, US Regulated [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									321	327	299
Electricity, US Regulated [Member] | 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									12	13	13
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									4,639	4,609	4,428
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									4,644	4,614	4,423
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,316	2,351	2,246
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									505	488	490
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,112	1,124	1,086
Electricity, US Regulated [Member] | 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									61	58	60
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									650	593	541
Electricity, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									10	10	8
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,258	2,233	2,126
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2,255	2,232	2,127
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,012	1,021	964
Electricity, US Regulated [Member] | 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									149	140	137
Electricity, US Regulated [Member] | 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									833	846	794
Electricity, US Regulated [Member] | 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									34	32	33
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									227	193	199
Electricity, US Regulated [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									8	7	5
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,143	1,139	1,125
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,148	1,144	1,130
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									645	669	663
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									186	186	187
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									99	100	103
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									14	14	14
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									204	175	163
Electricity, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									2	3	3
Electricity, US Regulated [Member] | Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,237	1,237	1,176
Electricity, US Regulated [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,240	1,240	1,178
Electricity, US Regulated [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									659	661	619
Electricity, US Regulated [Member] | 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									170	162	166
Electricity, US Regulated [Member] | 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									180	178	189
Electricity, US Regulated [Member] | 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									13	12	13
Electricity, US Regulated [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									218	227	191
Electricity, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1,489	1,470	1,333
Natural Gas, US Regulated [Member] | Operating Segments [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									167	181	161
Natural Gas, US Regulated [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									0	0	0
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									610	568	494
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									610	568	494
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									409	395	331
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									169	143	131
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1	1	1
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									25	23	23
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									6	6	8
Natural Gas, US Regulated [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									1	1	1
Natural Gas, US Regulated [Member] | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									700	738	652
Natural Gas, US Regulated [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									714	755	659
Natural Gas, US Regulated [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									474	491	437
Natural Gas, US Regulated [Member] | 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									77	77	75
Natural Gas, US Regulated [Member] | 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									132	124	119
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									31	63	28
Natural Gas, US Regulated [Member] | 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									4	4	4
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									167	181	161
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									166	180	160
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									96	99	90
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									44	44	38
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									5	8	8
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									14	16	15
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									7	13	9
Natural Gas, US Regulated [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									0	1	1
Natural Gas, US Regulated [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									0	0	0
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									167	181	161
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									167	180	160
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									96	99	90
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									45	44	38
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									5	8	8
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									14	16	15
Natural Gas, US Regulated [Member] | Delmarva Power & Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									7	13	9
Natural Gas, US Regulated [Member] | Delmarva Power & 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
Natural Gas, US Regulated [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									0	0	0
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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
Natural Gas, US Regulated [Member] | 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