Regulatory Matters Schedule of Completed Rate Cases (Details) (Details) - USD ($) $ in Millions														9 Months Ended	12 Months Ended
	Aug. 12, 2019	May 24, 2019	May 23, 2019	Apr. 08, 2019	Mar. 13, 2019	Jan. 15, 2019	Jan. 04, 2019	Dec. 20, 2018	Dec. 04, 2018	Nov. 19, 2018	Jun. 08, 2018	Apr. 16, 2018	Mar. 29, 2018	Sep. 30, 2019	Dec. 31, 2018
Commonwealth Edison Co [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)			$ 53											$ 21
Approved Return on Equity, Percentage														11.50%	10.91%
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)				$ (6)								$ (23)		$ 57
Approved Revenue Requirement Increase (Decrease)									$ (24)						$ (63)
Approved Return on Equity, Percentage									8.69%
PECO Energy Co [Member] | Electricity [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)													$ 82
Approved Revenue Requirement Increase (Decrease)								$ 25
Baltimore Gas and Electric Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)														$ (10)
Approved Return on Equity, Percentage														10.50%
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)		$ 74
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)		$ 59									$ 61
Approved Revenue Requirement Increase (Decrease)							$ 43
Approved Return on Equity, Percentage							9.80%
Atlantic City Electric Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)														$ 11
Approved Return on Equity, Percentage														10.50%
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)										$ 122
Approved Revenue Requirement Increase (Decrease)					$ 70
Approved Return on Equity, Percentage					9.60%
Potomac Electric Power Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)														$ 15
Approved Return on Equity, Percentage														10.50%
MARYLAND | Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)						$ 27
Approved Revenue Requirement Increase (Decrease)	$ 10
Approved Return on Equity, Percentage	9.60%