Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 104,212	$ 99,609
Less: accumulated depreciation	23,979	22,902
Property, plant and equipment, net	80,233	76,707
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 56,809	53,090
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	$ 29,839	29,170
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)	56 years
Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 6,147	5,530
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	$ 1,907	1,627
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	$ 5,656	5,957
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	$ 3,055	3,377
Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 799	858
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	$ 36,210	36,187
Less: accumulated depreciation	12,017	12,206
Property, plant and equipment, net	24,193	23,981
Nuclear fuel - work in progress	1,025	1,004
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	$ 29,839	29,170
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)	56 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	5,656	5,957
Less: accumulated depreciation	$ 2,867	2,969
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	$ 702	997
Exelon Generation Co L L C [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 13	63
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	$ 28,275	26,742
Less: accumulated depreciation	5,168	4,684
Property, plant and equipment, net	23,107	22,058
Commonwealth Edison Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 27,566	25,991
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	662	705
Commonwealth Edison Co [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 47	46
Commonwealth Edison Co [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)	34 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	$ 13,010	12,171
Less: accumulated depreciation	3,718	3,561
Property, plant and equipment, net	9,292	8,610
PECO Energy Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 8,957	8,359
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)	65 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	$ 2,899	2,694
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	$ 877	756
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)	50 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	250	343
PECO Energy Co [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 27	19
Average Service Life (years)	50 years
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 12,824	11,876
Less: accumulated depreciation	3,834	3,633
Property, plant and equipment, net	8,990	8,243
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 8,326	7,951
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)	75 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	$ 2,999	2,630
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	$ 991	860
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	483	410
Baltimore Gas and Electric Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 25	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	$ 15,509	14,287
Less: accumulated depreciation	1,213	841
Property, plant and equipment, net	14,296	13,446
Pepco Holdings LLC [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 13,809	12,664
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	$ 525	486
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	$ 146	126
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	921	912
Pepco Holdings LLC [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 108	99
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	$ 10,426	9,814
Less: accumulated depreciation	3,517	3,354
Property, plant and equipment, net	6,909	6,460
Potomac Electric Power Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 9,734	9,217
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	628	536
Potomac Electric Power Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 64	61
Potomac Electric Power Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)	33 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	$ 5,460	5,150
Less: accumulated depreciation	1,425	1,329
Property, plant and equipment, net	4,035	3,821
Delmarva Power & Light Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 4,464	4,195
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	$ 690	651
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	$ 160	136
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	125	151
Delmarva Power & Light Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 21	17
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	$ 4,400	4,103
Less: accumulated depreciation	1,210	1,137
Property, plant and equipment, net	3,190	2,966
Atlantic City Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 4,207	3,866
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	166	209
Atlantic City Electric Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 27	$ 28
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