Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 10,066	$ 10,392
Regulatory liabilities, current	581	406
Noncurrent regulatory liabilities	9,485	9,986
Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	4,502	4,944
Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3,016	3,102
Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,649	1,621
Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	175	109
Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	52	34
Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	221	582
Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	427
Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	24
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	6,692	6,742
Regulatory liabilities, current	289	200
Noncurrent regulatory liabilities	6,403	6,542
Commonwealth Edison Co [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,205	2,297
Commonwealth Edison Co [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,541	2,622
Commonwealth Edison Co [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,482	1,435
Commonwealth Edison Co [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	34	45
Commonwealth Edison Co [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2	6
Commonwealth Edison Co [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1	337
Commonwealth Edison Co [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	427	320
Commonwealth Edison Co [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	624	601
Regulatory liabilities, current	121	91
Noncurrent regulatory liabilities	503	510
PECO Energy Co [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
PECO Energy Co [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	475	480
PECO Energy Co [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
PECO Energy Co [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	97	56
PECO Energy Co [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	12	28
PECO Energy Co [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	40	37
PECO Energy Co [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
PECO Energy Co [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,139	1,228
Regulatory liabilities, current	30	33
Noncurrent regulatory liabilities	1,109	1,195
Baltimore Gas and Electric Company [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,001	1,089
Baltimore Gas and Electric Company [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	47	58
Baltimore Gas and Electric Company [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	6	0
Baltimore Gas and Electric Company [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	85	81
Baltimore Gas and Electric Company [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Baltimore Gas and Electric Company [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,575	1,777
Regulatory liabilities, current	137	70
Noncurrent regulatory liabilities	1,438	1,707
Pepco Holdings LLC [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,296	1,558
Pepco Holdings LLC [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Pepco Holdings LLC [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	120	128
Pepco Holdings LLC [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	38	8
Pepco Holdings LLC [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	38	0
Pepco Holdings LLC [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	59	83
Pepco Holdings LLC [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	24
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	690	754
Regulatory liabilities, current	46	8
Noncurrent regulatory liabilities	644	746
Potomac Electric Power Company [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	621	725
Potomac Electric Power Company [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Potomac Electric Power Company [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	20	20
Potomac Electric Power Company [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	24	0
Potomac Electric Power Company [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	23	0
Potomac Electric Power Company [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2	9
Noncurrent regulatory liabilities		746
Potomac Electric Power Company [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Potomac Electric Power Company [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Delmarva Power & Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	540	611
Regulatory liabilities, current	47	37
Noncurrent regulatory liabilities	493	574
Delmarva Power & Light Company [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	404	477
Delmarva Power & Light Company [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power & Light Company [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	100	108
Delmarva Power & Light Company [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	10	8
Delmarva Power & Light Company [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	9	0
Delmarva Power & Light Company [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	17	18
Delmarva Power & Light Company [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Delmarva Power & Light Company [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	318	382
Regulatory liabilities, current	44	25
Noncurrent regulatory liabilities	274	357
Atlantic City Electric Company [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	271	356
Atlantic City Electric Company [Member] | Nuclear decommissioning
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Removal costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Over Recovered Energy and Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	4	0
Atlantic City Electric Company [Member] | Transmission formula rate annual reconciliations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	6	0
Atlantic City Electric Company [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory Liabilities	13	$ 26
Atlantic City Electric Company [Member] | Renewable portfolio standards costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Atlantic City Electric Company [Member] | Stranded costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 24