Regulatory Matters - Schedule of Pending Rate Cases (Details) - USD ($) $ in Millions	Feb. 02, 2021	Dec. 09, 2020	Oct. 26, 2020	Oct. 09, 2020	Sep. 30, 2020	Jun. 01, 2020
Pennsylvania 2020 Natural Gas Distribution Base Rate Case | PECO Energy Co [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 69
Public Utilities, Requested Return on Equity, Percentage					10.95%
District of Columbia 2019 Electric Distribution Base Rate Case | Potomac Electric Power Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount						$ 136
Public Utilities, Requested Return on Equity, Percentage						9.70%
District of Columbia 2019 Electric Distribution Base Rate Case | Potomac Electric Power Company [Member] | 2022 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 73
District of Columbia 2019 Electric Distribution Base Rate Case | Potomac Electric Power Company [Member] | 2023 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 63
Maryland 2020 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 110
Public Utilities, Requested Return on Equity, Percentage			10.20%
Maryland 2020 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | 2023 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 56
Maryland 2020 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | 2024 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 54
Delaware 2020 Gas Distribution Base Rate Case | Delmarva Power & Light Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount				$ 7
Delaware 2020 Electric Distribution Base Rate Case | Delmarva Power & Light Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 23
Public Utilities, Requested Return on Equity, Percentage	10.30%
New Jersey 2020 Electric Distribution Base Rate Case | Atlantic City Electric Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 67
Public Utilities, Requested Return on Equity, Percentage		10.30%