Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Major Customer [Line Items]
Revenues	$ 7,915,000,000	$ 7,322,000,000	$ 17,805,000,000	$ 16,069,000,000
Revenue from Related Parties	0	1,000,000	0	2,000,000
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenues	1,517,000,000	1,417,000,000	3,052,000,000	2,856,000,000
Revenue from Related Parties	5,000,000	11,000,000	11,000,000	16,000,000
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,499,000,000	1,442,000,000	2,972,000,000	2,863,000,000
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	18,000,000	(25,000,000)	80,000,000	(7,000,000)
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenues	693,000,000	681,000,000	1,582,000,000	1,493,000,000
Revenue from Related Parties	2,000,000	2,000,000	4,000,000	4,000,000
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	686,000,000	678,000,000	1,565,000,000	1,485,000,000
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	7,000,000	3,000,000	17,000,000	8,000,000
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	682,000,000	616,000,000	1,656,000,000	1,554,000,000
Revenue from Related Parties	7,000,000	4,000,000	13,000,000	10,000,000
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	688,000,000	652,000,000	1,644,000,000	1,550,000,000
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(6,000,000)	(36,000,000)	12,000,000	4,000,000
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues	1,140,000,000	1,016,000,000	2,384,000,000	2,187,000,000
Revenue from Related Parties	4,000,000	3,000,000	7,000,000	7,000,000
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,098,000,000	1,080,000,000	2,296,000,000	2,233,000,000
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	42,000,000	(64,000,000)	88,000,000	(46,000,000)
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenues	523,000,000	494,000,000	1,076,000,000	1,039,000,000
Revenue from Related Parties	1,000,000	1,000,000	3,000,000	3,000,000
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	503,000,000	507,000,000	1,030,000,000	1,036,000,000
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	20,000,000	(13,000,000)	46,000,000	3,000,000
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenues	298,000,000	267,000,000	680,000,000	617,000,000
Revenue from Related Parties	2,000,000	2,000,000	4,000,000	4,000,000
Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	288,000,000	292,000,000	661,000,000	640,000,000
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	10,000,000	(25,000,000)	19,000,000	(23,000,000)
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	319,000,000	256,000,000	629,000,000	532,000,000
Revenue from Related Parties	1,000,000	1,000,000	1,000,000	1,000,000
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	307,000,000	282,000,000	606,000,000	557,000,000
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	12,000,000	(26,000,000)	23,000,000	(25,000,000)
Rate-regulated electric revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,787,000,000	3,475,000,000	7,775,000,000	7,222,000,000
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,503,000,000	1,431,000,000	2,977,000,000	2,853,000,000
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,499,000,000	1,442,000,000	2,972,000,000	2,863,000,000
Revenue from Related Parties	5,000,000	11,000,000	11,000,000	16,000,000
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9,000,000	0	16,000,000	6,000,000
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	759,000,000	767,000,000	1,502,000,000	1,468,000,000
Rate-regulated electric revenues [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	377,000,000	327,000,000	744,000,000	689,000,000
Rate-regulated electric revenues [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	138,000,000	119,000,000	271,000,000	253,000,000
Rate-regulated electric revenues [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	11,000,000	11,000,000	22,000,000	23,000,000
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	214,000,000	218,000,000	433,000,000	430,000,000
Rate-regulated electric revenues [Member] | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	602,000,000	580,000,000	1,251,000,000	1,180,000,000
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	603,000,000	582,000,000	1,254,000,000	1,181,000,000
Revenue from Related Parties	1,000,000	1,000,000	3,000,000	3,000,000
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	3,000,000
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	383,000,000	377,000,000	816,000,000	759,000,000
Rate-regulated electric revenues [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	99,000,000	88,000,000	199,000,000	187,000,000
Rate-regulated electric revenues [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	59,000,000	55,000,000	116,000,000	108,000,000
Rate-regulated electric revenues [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	8,000,000	7,000,000	17,000,000	14,000,000
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	54,000,000	55,000,000	106,000,000	113,000,000
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	560,000,000	530,000,000	1,180,000,000	1,125,000,000
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	561,000,000	532,000,000	1,182,000,000	1,128,000,000
Revenue from Related Parties	4,000,000	3,000,000	5,000,000	6,000,000
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,000,000	1,000,000	3,000,000	3,000,000
Rate-regulated electric revenues [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	299,000,000	304,000,000	662,000,000	644,000,000
Rate-regulated electric revenues [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	60,000,000	51,000,000	129,000,000	118,000,000
Rate-regulated electric revenues [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	108,000,000	94,000,000	213,000,000	198,000,000
Rate-regulated electric revenues [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	7,000,000	7,000,000	13,000,000	14,000,000
Rate-regulated electric revenues [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	87,000,000	76,000,000	165,000,000	154,000,000
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,071,000,000	1,047,000,000	2,195,000,000	2,133,000,000
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,074,000,000	1,050,000,000	2,202,000,000	2,139,000,000
Revenue from Related Parties	4,000,000	3,000,000	7,000,000	7,000,000
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,000,000	0	0	1,000,000
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	537,000,000	529,000,000	1,142,000,000	1,062,000,000
Rate-regulated electric revenues [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	124,000,000	105,000,000	242,000,000	221,000,000
Rate-regulated electric revenues [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	257,000,000	240,000,000	505,000,000	493,000,000
Rate-regulated electric revenues [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	17,000,000	15,000,000	30,000,000	30,000,000
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	139,000,000	161,000,000	283,000,000	333,000,000
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	503,000,000	506,000,000	1,027,000,000	1,034,000,000
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	503,000,000	507,000,000	1,030,000,000	1,036,000,000
Revenue from Related Parties	1,000,000	1,000,000	3,000,000	3,000,000
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,000,000	0	0	1,000,000
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	223,000,000	237,000,000	476,000,000	472,000,000
Rate-regulated electric revenues [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	32,000,000	29,000,000	65,000,000	65,000,000
Rate-regulated electric revenues [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	188,000,000	175,000,000	372,000,000	363,000,000
Rate-regulated electric revenues [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	10,000,000	8,000,000	16,000,000	17,000,000
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	50,000,000	58,000,000	101,000,000	119,000,000
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	262,000,000	260,000,000	562,000,000	543,000,000
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	264,000,000	262,000,000	566,000,000	546,000,000
Revenue from Related Parties	2,000,000	2,000,000	4,000,000	4,000,000
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	1,000,000
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	147,000,000	147,000,000	337,000,000	308,000,000
Rate-regulated electric revenues [Member] | 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	46,000,000	39,000,000	92,000,000	82,000,000
Rate-regulated electric revenues [Member] | 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	22,000,000	22,000,000	43,000,000	45,000,000
Rate-regulated electric revenues [Member] | 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	3,000,000	3,000,000	7,000,000	6,000,000
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	46,000,000	51,000,000	87,000,000	105,000,000
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	306,000,000	281,000,000	605,000,000	556,000,000
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	307,000,000	282,000,000	606,000,000	557,000,000
Revenue from Related Parties	1,000,000	1,000,000	1,000,000
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	167,000,000	145,000,000	329,000,000	282,000,000
Rate-regulated electric revenues [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	46,000,000	37,000,000	85,000,000	74,000,000
Rate-regulated electric revenues [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	47,000,000	43,000,000	90,000,000	85,000,000
Rate-regulated electric revenues [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	4,000,000	4,000,000	7,000,000	7,000,000
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	43,000,000	53,000,000	95,000,000	109,000,000
Rate-regulated natural gas revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	228,000,000	236,000,000	865,000,000	832,000,000
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	82,000,000	95,000,000	310,000,000	304,000,000
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	83,000,000	96,000,000	311,000,000	304,000,000
Revenue from Related Parties	0	0	1,000,000
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	(1,000,000)	0	0
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	55,000,000	70,000,000	215,000,000	220,000,000
Rate-regulated natural gas revenues [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	22,000,000	19,000,000	81,000,000	70,000,000
Rate-regulated natural gas revenues [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	0	0	0	0
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,000,000	6,000,000	12,000,000	12,000,000
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,000,000	1,000,000	3,000,000	2,000,000
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	125,000,000	119,000,000	455,000,000	419,000,000
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	127,000,000	120,000,000	462,000,000	422,000,000
Revenue from Related Parties	3,000,000	1,000,000	7,000,000	4,000,000
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,000,000	0	1,000,000	1,000,000
Rate-regulated natural gas revenues [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	81,000,000	81,000,000	297,000,000	287,000,000
Rate-regulated natural gas revenues [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	13,000,000	12,000,000	48,000,000	46,000,000
Rate-regulated natural gas revenues [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	27,000,000	24,000,000	81,000,000	76,000,000
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	6,000,000	3,000,000	36,000,000	13,000,000
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	24,000,000	30,000,000	94,000,000	94,000,000
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	24,000,000	30,000,000	94,000,000	94,000,000
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,000,000	17,000,000	57,000,000	57,000,000
Rate-regulated natural gas revenues [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	6,000,000	8,000,000	24,000,000	25,000,000
Rate-regulated natural gas revenues [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	1,000,000	1,000,000	3,000,000	2,000,000
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,000,000	3,000,000	8,000,000	7,000,000
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,000,000	1,000,000	2,000,000	3,000,000
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	24,000,000	30,000,000	95,000,000	94,000,000
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	24,000,000	30,000,000	95,000,000	94,000,000
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,000,000	17,000,000	57,000,000	57,000,000
Rate-regulated natural gas revenues [Member] | 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	6,000,000	8,000,000	24,000,000	25,000,000
Rate-regulated natural gas revenues [Member] | 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	1,000,000	1,000,000	3,000,000	2,000,000
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,000,000	3,000,000	8,000,000	7,000,000
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,000,000	1,000,000	3,000,000	3,000,000
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Rate-regulated natural gas revenues [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	0
Alternative revenue programs [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9,000,000	(25,000,000)	64,000,000	(13,000,000)
Alternative revenue programs [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7,000,000	4,000,000	17,000,000	5,000,000
Alternative revenue programs [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(10,000,000)	(37,000,000)	8,000,000	0
Alternative revenue programs [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	41,000,000	(64,000,000)	88,000,000	(47,000,000)
Alternative revenue programs [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	19,000,000	(13,000,000)	46,000,000	2,000,000
Alternative revenue programs [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10,000,000	(25,000,000)	19,000,000	(24,000,000)
Alternative revenue programs [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 12,000,000	$ (26,000,000)	$ 23,000,000	$ (25,000,000)