Segment Information Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues			$ 0				$ 0
Rate-regulated natural gas revenues			0				0
Revenues from alternative revenue programs	$ (25)		54		$ (41)		191
Revenues	9,403		8,768		27,170		25,180
Revenue from Related Parties	0	[1]	0	[1]	0	[2]	0
Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	4,270	[3]	4,164	[3]	11,766	[4]	11,318	[4]
Rate-regulated natural gas revenues	162	[3]	149	[3]	1,017	[4]	906	[4]
Revenues	9,403	[3]	8,768	[3]	27,170	[4]	25,180	[4]
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	1,609		1,552		4,512		4,167
Rate-regulated natural gas revenues			0				0
Revenues from alternative revenue programs	(15)		16		(27)		48
Revenues	1,598		1,571		4,508		4,227
Revenue from Related Parties	4		3		23		12
Commonwealth Edison Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	(15)		16		(27)		48
Revenues			0				0
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	1,606	[5]	1,547	[5]	4,512	[6]	4,156	[6]
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	7	[7]	8	[7]	23	[8]	23	[8]
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	861		816		2,277		2,071
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	391		366		1,132		1,035
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	131		119		411		346
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	11		11		36		33
Commonwealth Edison Co [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	212	[9]	235	[9]	656	[10]	671	[10]
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[11]	0	[11]	0	[12]	0	[12]
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[7]	0	[7]	0	[8]	0	[8]
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues					0		0
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Commonwealth Edison Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[13]	0	[13]	0	[14]	0	[14]
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,606		1,547		4,512		4,156
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(8)		24		(4)		71
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	697		660		1,886		1,798
Rate-regulated natural gas revenues	57		53		382		338
Revenues from alternative revenue programs	1		0		2		0
Revenues	757		715		2,275		2,141
Revenue from Related Parties	2		2		5		5
PECO Energy Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	1		0		2		0
Revenues			0				0
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	696	[5]	659	[5]	1,881	[6]	1,792	[6]
Revenue from Related Parties	2		1		5		4
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	3	[7]	3	[7]	10	[8]	10	[8]
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	458		434		1,199		1,147
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	108		106		306		303
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	64		59		174		168
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	7		7		21		23
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	59	[9]	53	[9]	181	[10]	151	[10]
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	57	[11]	53	[11]	382	[12]	339	[12]
Revenue from Related Parties	0		0		0		0
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[7]	0	[7]	0	[8]	0	[8]
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	36		33		259		225
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	15		14		102		90
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		1		0
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	5		5		16		16
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	1	[13]	1	[13]	4	[14]	8	[14]
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	753		712		2,263		2,131
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	4		3		12		10
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	652		626		1,847		1,811
Rate-regulated natural gas revenues	79		73		527		438
Revenues from alternative revenue programs	(6)		36		(23)		102
Revenues	731		738		2,369		2,363
Revenue from Related Parties	6		3		18		12
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	(6)		36		(23)		102
Revenues			0				0
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	649	[5]	624	[5]	1,842	[6]	1,805	[6]
Revenue from Related Parties	1		1		5		5
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	4	[7]	3	[7]	10	[8]	11	[8]
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	366		352		1,054		1,038
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	68		65		196		193
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	117		114		325		329
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	7		8		21		23
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	91	[9]	85	[9]	246	[10]	222	[10]
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	83	[11]	74	[11]	537	[12]	442	[12]
Revenue from Related Parties	5		2		13		7
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	1	[7]	1	[7]	3	[8]	3	[8]
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	46		44		345		289
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	8		8		55		51
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	17		19		88		82
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	12	[13]	3	[13]	49	[14]	20	[14]
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	732		698		2,379		2,247
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(1)		40		(10)		116
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	1,340		1,278		3,541		3,376
Rate-regulated natural gas revenues	23		18		129		105
Revenues from alternative revenue programs	(5)		2		7		41
Revenues	1,361		1,310		3,688		3,557
Revenue from Related Parties	3		12		11		35
Pepco Holdings LLC [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	(5)		2		7		41
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	1,339	[5]	1,276	[5]	3,544	[6]	3,370	[6]
Revenue from Related Parties			1				2
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	3	[7]	3	[7]	8	[8]	8	[8]
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	726		687		1,839		1,740
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	140		140		370		373
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	303		288		845		814
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	14		14		44		45
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	156	[9]	147	[9]	446	[10]	398	[10]
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	24	[11]	18	[11]	129	[12]	105	[12]
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[7]	0	[7]	0	[8]	0	[8]
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	8		8		68		57
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	5		3		31		25
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	2		1		7		5
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	3		3		12		11
Pepco Holdings LLC [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	6	[13]	3	[13]	11	[14]	7	[14]
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,363		1,294		3,673		3,475
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(2)		16		15		82
Revenue from Related Parties			11	[15]			33	[16]
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	630		600		1,697		1,622
Rate-regulated natural gas revenues			0				0
Revenues from alternative revenue programs	(4)		3		6		23
Revenues	628		604		1,708		1,649
Revenue from Related Parties	2		1		5		4
Potomac Electric Power Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	(4)		3		6		23
Revenues			0				0
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	630	[5]	599	[5]	1,697	[6]	1,621	[6]
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	2	[7]	2	[7]	5	[8]	5	[8]
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	306		291		792		751
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	39		37		104		105
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	230		211		632		593
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	8		8		24		24
Potomac Electric Power Company [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	47	[9]	52	[9]	145	[10]	148	[10]
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[11]	0	[11]	0	[12]	0	[12]
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[7]	0	[7]	0	[8]	0	[8]
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Potomac Electric Power Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[13]	0	[13]	0	[14]	0	[14]
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	630		599		1,697		1,621
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(2)		5		11		28
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	302		308		861		851
Rate-regulated natural gas revenues	24		18		129		105
Revenues from alternative revenue programs	0		(1)		5		9
Revenues	328		327		1,001		971
Revenue from Related Parties	2		2		6		6
Delmarva Power and Light Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	0		(1)		5		9
Revenues			0				0
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	303	[5]	309	[5]	864	[6]	854	[6]
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	1	[7]	1	[7]	3	[8]	3	[8]
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	180		185		513		505
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	48		50		138		139
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	25		28		74		78
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	3		3		10		11
Delmarva Power and Light Company [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	47	[9]	43	[9]	129	[10]	121	[10]
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	24	[11]	18	[11]	129	[12]	105	[12]
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[7]	0	[7]	0	[8]	0	[8]
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	8		8		68		57
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	5		3		31		25
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	2		1		7		5
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	3		3		12		11
Delmarva Power and Light Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	6	[13]	3	[13]	11	[14]	7	[14]
Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	327		327		993		959
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	1		0		8		12
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	406		370		983		904
Rate-regulated natural gas revenues			0				0
Revenues from alternative revenue programs	(1)		0		(4)		9
Revenues	406		370		981		915
Revenue from Related Parties	1		0		2		2
Atlantic City Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues from alternative revenue programs	(1)		0		(4)		9
Revenues			0				0
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	407	[5]	370	[5]	985	[6]	906	[6]
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	0	[7]	0	[7]	0	[8]	0	[8]
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	240		211		534		484
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	53		53		128		129
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	48		49		139		143
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	3		3		10		10
Atlantic City Electric Company [Member] | Rate-Regulated Electric Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated electric revenues	63	[9]	54	[9]	174	[10]	140	[10]
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[11]	0	[11]	0	[12]	0	[12]
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[7]	0	[7]	0	[8]	0	[8]
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0		0		0		0
Atlantic City Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Rate-regulated natural gas revenues	0	[13]	0	[13]	0	[14]	0	[14]
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	407		370		985		906
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	$ (1)		0		$ (4)		$ 9
Atlantic City Electric Co Affiliate [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties			$ 0

[1] Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.

[2] Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.

[3] Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for total utility taxes for the three months ended September 30, 2018 and 2017.

[4] Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for total utility taxes for the nine months ended September 30, 2018 and 2017.

[5] Includes operating revenues from affiliates of $4 million, $2 million, $1 million, $3 million, $2 million, $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, for the three months ended September 30, 2018 and $3 million, $1 million, $1 million, $1 million $1 million, $2 million and less than $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, for the three months ended September 30, 2017.

[6] Includes operating revenues from affiliates of $23 million, $5 million, $5 million, $11 million, $5 million, $6 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, for the nine months ended September 30, 2018 and $12 million, $4 million, $5 million, $2 million, $4 million, $6 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, for the nine months ended September 30, 2017.

[7] Includes late payment charge revenues.

[8] Includes late payment charge revenues.

[9] Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue.

[10] Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue.

[11] Includes operating revenues from affiliates of less than $1 million and $5 million at PECO and BGE, respectively, for the three months ended September 30, 2018 and less than $1 million and $2 million at PECO and BGE, respectively, for the three months ended September 30, 2017.

[12] Includes operating revenues from affiliates of less than $1 million and $13 million at PECO and BGE, respectively, for the nine months ended September 30, 2018 and less than $1 million and $7 million at PECO and BGE, respectively, for the nine months ended September 30, 2017.

[13] Includes revenues from off-system natural gas sales.

[14] Includes revenues from off-system natural gas sales.

[15] Includes operating revenues from affiliates of $11 million at PHI for the three months ended September 30, 2017.

[16] Includes operating revenues from affiliates of $33 million at PHI for the nine months ended September 30, 2017.