Regulatory Matters Regulatory Matters - Annual Electric Distribution/Transmission Filings (Details) - USD ($) $ in Millions																									12 Months Ended
		Jan. 15, 2019	Dec. 04, 2018	Nov. 19, 2018	Sep. 07, 2018	Aug. 21, 2018	Jun. 27, 2018	May 31, 2018	Apr. 20, 2018	[4]	Apr. 17, 2018		Apr. 16, 2018	Mar. 08, 2018	[4]	Mar. 02, 2018	Feb. 09, 2018		Feb. 06, 2018	Jan. 31, 2018	Jan. 18, 2018	Dec. 19, 2017	Dec. 18, 2017	Nov. 16, 2017	Dec. 31, 2018	Dec. 31, 2017
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]																								$ (44)
Tax Savings From Tax Cuts and Jobs Act																					$ 201
Prior Year Revenue Adjustment	[1]																								$ 18
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint																									55.00%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]																								$ (26)
Public Utilities, Approved Equity Capital Structure, Percentage	[1]																								8.32%
Public Utilities, Approved Return on Equity, Percentage	[1],[3]																								11.50%
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																									$ (58)
Public Utilities, Approved Rate Increase (Decrease), Amount																										$ 34
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]		$ (24)										$ (23)
Public Utilities, Approved Equity Capital Structure, Percentage																									6.52%
Public Utilities, Requested Equity Capital Structure, Percentage			8.69%
Commonwealth Edison Co [Member] | Electric Transmission [Member]
Public Utilities, General Disclosures [Line Items]
Tax Savings From Tax Cuts and Jobs Act																									$ 69
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]																								10
Prior Year Revenue Adjustment	[1]																								4
Proposed Capital Expenditure																									12
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2],[5]																								$ 26
Public Utilities, Approved Equity Capital Structure, Percentage	[1]																								7.61%
Public Utilities, Approved Return on Equity, Percentage																									10.50%
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Tax Savings From Tax Cuts and Jobs Act																				$ 72
Baltimore Gas and Electric Company [Member] | Electric Transmission [Member]
Public Utilities, General Disclosures [Line Items]
Tax Savings From Tax Cuts and Jobs Act																									$ 18
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																									6
Prior Year Revenue Adjustment																									2
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[2]																								$ 8
Public Utilities, Approved Equity Capital Structure, Percentage																									7.82%
Public Utilities, Approved Return on Equity, Percentage	[3]																								10.50%
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 30																				$ 66
Tax Savings From Tax Cuts and Jobs Act																			$ 39
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					$ 4				$ (15)		$ (24)	[4]		$ 3
Public Utilities, Requested Return on Equity, Percentage		10.30%						9.50%			9.525%
Potomac Electric Power Company [Member] | Electric Transmission [Member]
Public Utilities, General Disclosures [Line Items]
Tax Savings From Tax Cuts and Jobs Act																									$ 13
Delmarva Power & Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																									14
Prior Year Revenue Adjustment																									13
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[2]																								$ 27
Public Utilities, Approved Equity Capital Structure, Percentage																									7.29%
Public Utilities, Approved Return on Equity, Percentage	[3]																								10.50%
Delmarva Power & Light Company [Member] | Electric Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]						$ (7)
Tax Savings From Tax Cuts and Jobs Act																	$ 19
Public Utilities, Approved Rate Increase (Decrease), Amount																							$ 13
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																	$ 12	[4]						$ 19
Public Utilities, Approved Return on Equity, Percentage																							9.50%
Public Utilities, Requested Return on Equity, Percentage							9.70%
Delmarva Power & Light Company [Member] | Electric Transmission [Member]
Public Utilities, General Disclosures [Line Items]
Tax Savings From Tax Cuts and Jobs Act																									$ 12
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 40																			4
Tax Savings From Tax Cuts and Jobs Act																$ 23
Prior Year Revenue Adjustment																									(4)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[2]																								$ 0
Public Utilities, Approved Equity Capital Structure, Percentage																									8.02%
Public Utilities, Approved Return on Equity, Percentage	[3]																								10.50%
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[6]			$ 122
Public Utilities, Requested Return on Equity, Percentage						10.10%
Atlantic City Electric Company [Member] | Electric Transmission [Member]
Public Utilities, General Disclosures [Line Items]
Tax Savings From Tax Cuts and Jobs Act																									$ 11

[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.

[6] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVlYzRiNDIxOTkxNDRkN2ViNWYzYTRhOTVmMjFkNDYzfFRleHRTZWxlY3Rpb246NUYyM0EwMDI1MDhGQUUyMUZEMzExNTNGOUY0NjExNDUM}