Regulatory Matters Regulatory Matters - Schedule of Completed Rate Cases (Details) - USD ($) $ in Millions																							12 Months Ended		60 Months Ended
		Jan. 15, 2019	Jan. 04, 2019	Dec. 20, 2018	Dec. 04, 2018	Sep. 07, 2018	Jun. 27, 2018	Jun. 08, 2018	May 31, 2018	Apr. 20, 2018	[4]	Apr. 17, 2018		Apr. 16, 2018	Mar. 29, 2018	Mar. 08, 2018	[4]	Feb. 09, 2018		Dec. 19, 2017	Dec. 18, 2017	Nov. 16, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2023
Commonwealth Edison Co [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]																						$ (26)
Public Utilities, Approved Equity Capital Structure, Percentage	[1]																						8.32%
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]																						$ (44)
Public Utilities, Approved Return on Equity, Percentage	[1],[3]																						11.50%
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]				$ (24)									$ (23)
Public Utilities, Approved Rate Increase (Decrease), Amount																								$ 34
Public Utilities, Approved Equity Capital Structure, Percentage																							6.52%
Public Utilities, Requested Equity Capital Structure, Percentage					8.69%
Public Utilities, Requested Rate Increase (Decrease), Amount																							$ (58)
PECO Energy Co [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																							$ 22
Public Utilities, Requested Equity Capital Structure, Percentage																							11.00%
PECO Energy Co [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]			$ 25
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]														$ 82
Baltimore Gas and Electric Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2],[5]																						$ 26
Public Utilities, Approved Equity Capital Structure, Percentage	[1]																						7.61%
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]																						$ 10
Public Utilities, Approved Return on Equity, Percentage																							10.50%
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 43
Public Utilities, Requested Rate Increase (Decrease), Amount								$ 61
Public Utilities, Requested Return on Equity, Percentage			9.80%
Potomac Electric Power Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[2]																						$ 8
Public Utilities, Approved Equity Capital Structure, Percentage																							7.82%
Public Utilities, Requested Rate Increase (Decrease), Amount																							$ 6
Public Utilities, Approved Return on Equity, Percentage	[3]																						10.50%
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount						$ 4				$ (15)		$ (24)	[4]			$ 3
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 30																		$ 66
Public Utilities, Requested Return on Equity, Percentage		10.30%							9.50%			9.525%
Delmarva Power & Light Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[2]																						$ 27
Public Utilities, Approved Equity Capital Structure, Percentage																							7.29%
Public Utilities, Requested Rate Increase (Decrease), Amount																							$ 14
Public Utilities, Approved Return on Equity, Percentage	[3]																						10.50%
Delmarva Power & Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																		$ 12	[4]			$ 19
Public Utilities, Approved Rate Increase (Decrease), Amount																					$ 13
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]						$ (7)
Public Utilities, Requested Return on Equity, Percentage							9.70%
Public Utilities, Approved Return on Equity, Percentage																					9.50%
Delmarva Power & Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																	$ 4
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]					$ (4)
Public Utilities, Requested Return on Equity, Percentage						9.70%
Subsequent Event [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																									$ 200

[1] The time period for any formal challenges to the annual transmission formula rate update filings expired with no formal challenges submitted.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVlYzRiNDIxOTkxNDRkN2ViNWYzYTRhOTVmMjFkNDYzfFRleHRTZWxlY3Rpb246MzY0MUFFQzNGNTE3Mzk3OTI2RjIxNTRFRUQyNkYyMzMM}

[3] As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50%, inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55%. As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL and ACE, the rate of return on common equity is 10.50%, inclusive of a 50-basis-point incentive adder for being a member of a RTO.

[4] Includes the annual ongoing TCJA tax savings further discussed below.

[5] BGE's transmission revenue requirement includes a FERC approved dedicated facilities charge of $12 million to recover the costs of providing transmission service to specifically designated load by BGE.