Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 109,311	$ 104,212
Accumulated depreciation and amortization	26,727	23,979
Property, plant, and equipment, net	82,584	80,233
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 60,946	56,809
Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	80 years
Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 29,725	29,839
Electric—generation | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	1 year
Electric—generation | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	58 years
Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 6,733	6,147
Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	80 years
Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 2,170	1,907
Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	4 years
Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 5,399	5,656
Nuclear Fuel [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	1 year
Nuclear Fuel [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	8 years
Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 3,576	3,055
Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 762	799
Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	1 year
Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 35,584	36,210
Accumulated depreciation and amortization	13,370	12,017
Property, plant, and equipment, net	22,214	24,193
Nuclear fuel - work in progress	939	1,025
Exelon Generation Co L L C [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Exelon Generation Co L L C [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 29,724	29,839
Exelon Generation Co L L C [Member] | Electric—generation | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	1 year
Exelon Generation Co L L C [Member] | Electric—generation | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	58 years
Exelon Generation Co L L C [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Exelon Generation Co L L C [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Exelon Generation Co L L C [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	5,399	5,656
Accumulated depreciation and amortization	$ 2,774	2,867
Exelon Generation Co L L C [Member] | Nuclear Fuel [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	1 year
Exelon Generation Co L L C [Member] | Nuclear Fuel [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	8 years
Exelon Generation Co L L C [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 450	702
Exelon Generation Co L L C [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 11	13
Exelon Generation Co L L C [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	1 year
Exelon Generation Co L L C [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	10 years
Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 30,229	28,275
Accumulated depreciation and amortization	5,672	5,168
Property, plant, and equipment, net	24,557	23,107
Commonwealth Edison Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 29,371	27,566
Commonwealth Edison Co [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Commonwealth Edison Co [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	80 years
Commonwealth Edison Co [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Commonwealth Edison Co [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Commonwealth Edison Co [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Commonwealth Edison Co [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Commonwealth Edison Co [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	799	662
Commonwealth Edison Co [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 59	47
Commonwealth Edison Co [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	33 years
Commonwealth Edison Co [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
PECO Energy Co [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 14,024	13,010
Accumulated depreciation and amortization	3,843	3,718
Property, plant, and equipment, net	10,181	9,292
PECO Energy Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 9,462	8,957
PECO Energy Co [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
PECO Energy Co [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	70 years
PECO Energy Co [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
PECO Energy Co [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 3,098	2,899
PECO Energy Co [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
PECO Energy Co [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	70 years
PECO Energy Co [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 956	877
PECO Energy Co [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
PECO Energy Co [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	55 years
PECO Energy Co [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
PECO Energy Co [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	474	250
PECO Energy Co [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 34	27
Average  Service Life (years)	50 years
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 13,906	12,824
Accumulated depreciation and amortization	4,034	3,834
Property, plant, and equipment, net	9,872	8,990
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 8,797	8,326
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	80 years
Baltimore Gas and Electric Company [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 3,315	2,999
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	80 years
Baltimore Gas and Electric Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 1,138	991
Baltimore Gas and Electric Company [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	4 years
Baltimore Gas and Electric Company [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
Baltimore Gas and Electric Company [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Baltimore Gas and Electric Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	627	483
Baltimore Gas and Electric Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 29	25
Baltimore Gas and Electric Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	20 years
Baltimore Gas and Electric Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
Pepco Holdings LLC [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 17,188	15,509
Accumulated depreciation and amortization	1,811	1,213
Property, plant, and equipment, net	15,377	14,296
Pepco Holdings LLC [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 15,137	13,809
Pepco Holdings LLC [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Pepco Holdings LLC [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Pepco Holdings LLC [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Pepco Holdings LLC [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 591	525
Pepco Holdings LLC [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Pepco Holdings LLC [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Pepco Holdings LLC [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 178	146
Pepco Holdings LLC [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Pepco Holdings LLC [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Pepco Holdings LLC [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Pepco Holdings LLC [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	1,174	921
Pepco Holdings LLC [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 108	108
Pepco Holdings LLC [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	3 years
Pepco Holdings LLC [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
Potomac Electric Power Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 11,153	10,426
Accumulated depreciation and amortization	3,697	3,517
Property, plant, and equipment, net	7,456	6,909
Potomac Electric Power Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 10,264	9,734
Potomac Electric Power Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Potomac Electric Power Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Potomac Electric Power Company [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Potomac Electric Power Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Potomac Electric Power Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Potomac Electric Power Company [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Potomac Electric Power Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	824	628
Potomac Electric Power Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 65	64
Potomac Electric Power Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	25 years
Potomac Electric Power Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
Delmarva Power & Light Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 5,847	5,460
Accumulated depreciation and amortization	1,533	1,425
Property, plant, and equipment, net	4,314	4,035
Delmarva Power & Light Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 4,730	4,464
Delmarva Power & Light Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Delmarva Power & Light Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	70 years
Delmarva Power & Light Company [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Delmarva Power & Light Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 751	690
Delmarva Power & Light Company [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Delmarva Power & Light Company [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Delmarva Power & Light Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 180	160
Delmarva Power & Light Company [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Delmarva Power & Light Company [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	75 years
Delmarva Power & Light Company [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Delmarva Power & Light Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	163	125
Delmarva Power & Light Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 23	21
Delmarva Power & Light Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	8 years
Delmarva Power & Light Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	50 years
Atlantic City Electric Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 4,778	4,400
Accumulated depreciation and amortization	1,303	1,210
Property, plant, and equipment, net	3,475	3,190
Atlantic City Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 4,568	4,207
Atlantic City Electric Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	5 years
Atlantic City Electric Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	65 years
Atlantic City Electric Company [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 0	0
Atlantic City Electric Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Atlantic City Electric Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Atlantic City Electric Company [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	0
Atlantic City Electric Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	182	166
Atlantic City Electric Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 28	$ 27
Atlantic City Electric Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	13 years
Atlantic City Electric Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average  Service Life (years)	15 years