Regulatory Matters - Narrative (Details) - USD ($) $ in Millions																																	3 Months Ended			7 Months Ended	9 Months Ended			12 Months Ended		48 Months Ended	60 Months Ended
		Sep. 07, 2018	Aug. 29, 2018	Aug. 28, 2018	Aug. 21, 2018	Aug. 13, 2018	Jul. 01, 2018	Jun. 27, 2018	Jun. 15, 2018	Jun. 08, 2018	Jun. 02, 2018	May 22, 2018	Apr. 20, 2018	Apr. 17, 2018	Mar. 29, 2018	Mar. 26, 2018	Mar. 17, 2018	Mar. 08, 2018	Mar. 02, 2018	Feb. 09, 2018	Feb. 06, 2018	Feb. 05, 2018	Jan. 31, 2018	Jan. 18, 2018	Jan. 02, 2018	Dec. 19, 2017	Dec. 18, 2017	Nov. 16, 2017	Oct. 18, 2017	Aug. 17, 2017	Jul. 14, 2017	May 01, 2017	Sep. 30, 2018		Sep. 30, 2017	Dec. 31, 2017	Sep. 30, 2018		Sep. 30, 2017	Dec. 31, 2018		Dec. 31, 2022	Dec. 31, 2023	Jun. 30, 2018	Apr. 21, 2016
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	$ 9,342.0			$ 9,288.0	$ 9,342.0
Regulatory Liabilities																																	10,445.0			10,388.0	10,445.0
Revenues																																	9,403.0		$ 8,768.0		27,170.0		$ 25,180.0
Payments to Acquire Property, Plant, and Equipment																																					5,497.0		5,556.0
Other Receivables																																	1,246.0			1,132.0	1,246.0
Accounts Payable, Current																																	3,348.0			3,532.0	3,348.0
PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												$ 220.0
Accounts Payable, Current																																												176.0
Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	73.0				73.0
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																																	5,278.0		4,750.0		15,368.0		13,843.0
Payments to Acquire Property, Plant, and Equipment																																					1,660.0		1,654.0
License Costs																																					35.0
Other Receivables																																	278.0			321.0	278.0
Accounts Payable, Current																																	1,450.0			1,773.0	1,450.0
Exelon Generation Co L L C [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												0.0
Accounts Payable, Current																																												41.0
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																																													$ 3.0
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																																													$ 7.0
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	1,485.0			1,279.0	1,485.0
Regulatory Liabilities																																	6,638.0			6,577.0	6,638.0
Tax Savings From Tax Cuts and Jobs Act																								$ 201.0
Revenues																																	1,598.0		1,571.0		$ 4,508.0		4,227.0
Public Utilities, Requested Increase (Decrease), Amount											$ 38.0																													$ (44.0)	[1],[2]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount											1.0																													(26.0)	[1],[2]
Prior Year Revenue Adjustment																																								$ 18.0
Public Utilities, Approved Rate Increase (Decrease), Amount											$ (39.0)
Public Utilities, Approved Return on Equity, Percentage	[1],[2],[3]																																				11.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2],[4]																																							8.32%
Payments to Acquire Property, Plant, and Equipment																																					$ 1,540.0		1,698.0
Other Receivables																																	450.0			266.0	450.0
Accounts Payable, Current																																	576.0			568.0	$ 576.0
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Increase (Decrease), Amount																																								$ 58.0
Public Utilities, Requested Rate Increase (Decrease), Percentage																																								8.69%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																								$ 23.0
Public Utilities, Requested Equity Capital Structure, Percentage																																								6.52%
Commonwealth Edison Co [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												122.0
Accounts Payable, Current																																												0.0
Commonwealth Edison Co [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																								$ 69.0
Public Utilities, Approved Return on Equity, Percentage																																					55.00%
Commonwealth Edison Co [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	51.0				$ 51.0
Commonwealth Edison Co [Member] | Subsequent Event [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount																																								$ (35.0)
Public Utilities, Approved Rate Increase (Decrease), Percentage																																								8.69%
Public Utilities, Approved Equity Capital Structure, Percentage																																								6.52%
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	532.0			410.0	532.0
Regulatory Liabilities																																	740.0			690.0	740.0
Tax Savings From Tax Cuts and Jobs Act															$ 71.0
Revenues																																	757.0		715.0		2,275.0		2,141.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																$ 22.0
Public Utilities, Requested Equity Capital Structure, Percentage																																11.00%
Prior Year Revenue Adjustment																																					6.0
Payments to Acquire Property, Plant, and Equipment																																					615.0		537.0
Other Receivables																																	190.0			105.0	190.0
Accounts Payable, Current																																	387.0			370.0	387.0
PECO Energy Co [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act							$ 4.0
PECO Energy Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																							$ 68.0
Public Utilities, Requested Increase (Decrease), Amount				$ 25.0											$ 82.0
Public Utilities, Requested Equity Capital Structure, Percentage															10.95%
PECO Energy Co [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												85.0
Accounts Payable, Current																																												0.0
PECO Energy Co [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																					20.0
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	597.0			571.0	597.0
Regulatory Liabilities																																	1,165.0			1,163.0	1,165.0
Tax Savings From Tax Cuts and Jobs Act																							103.0
Revenues																																	731.0		738.0		$ 2,369.0		2,363.0
Public Utilities, Requested Increase (Decrease), Amount	[1],[2]																																							$ 10.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]																																							26.0
Prior Year Revenue Adjustment	[1],[2]																																							$ 4.0
Public Utilities, Approved Return on Equity, Percentage	[1],[2],[3]																																				10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2],[4]																																							7.61%
Payments to Acquire Property, Plant, and Equipment																																					$ 667.0		615.0
Other Receivables																																	96.0			94.0	96.0
Accounts Payable, Current																																	277.0			265.0	277.0
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																							31.0
Public Utilities, Requested Increase (Decrease), Amount										$ 61.0
Public Utilities, Requested Return on Equity, Percentage										10.50%
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																							$ 72.0
Baltimore Gas and Electric Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												0.0
Accounts Payable, Current																																												51.0
Baltimore Gas and Electric Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																								$ 18.0
Baltimore Gas and Electric Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	13.0				13.0
Baltimore Gas and Electric Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount																																											$ (200.0)
Payments to Acquire Property, Plant, and Equipment																																											$ 732.0
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	2,895.0			3,047.0	2,895.0
Regulatory Liabilities																																	1,882.0			1,928.0	1,882.0
Revenues																																	1,361.0		1,310.0		3,688.0		3,557.0
Payments to Acquire Property, Plant, and Equipment																																					988.0		995.0
Other Receivables																																	266.0			206.0	266.0
Accounts Payable, Current																																	505.0			348.0	505.0
Pepco Holdings LLC [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												13.0
Accounts Payable, Current																																												84.0
Pepco Holdings LLC [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	9.0				9.0
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	946.0			891.0	946.0
Regulatory Liabilities																																	764.0			832.0	764.0
Revenues																																	628.0		604.0		1,708.0		1,649.0
Public Utilities, Requested Increase (Decrease), Amount	[1],[2]																																							6.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]																																							8.0
Prior Year Revenue Adjustment	[1],[2]																																							$ 2.0
Public Utilities, Approved Return on Equity, Percentage	[1],[2],[3]																																							10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2],[4]																																							7.82%
Payments to Acquire Property, Plant, and Equipment																																					475.0		439.0
Other Receivables																																	102.0			87.0	102.0
Accounts Payable, Current																																	234.0			139.0	234.0
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																					$ 39.0
Tax Savings From Tax Cuts and Jobs Act Through Effective Date		$ (20.0)				$ (19.0)
Public Utilities, Requested Increase (Decrease), Amount																						$ 11.0			$ 41.0	$ 66.0
Public Utilities, Requested Rate Increase (Decrease), Percentage													9.50%												10.10%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount													$ 15.0	$ (24.0)				$ 3.0
Public Utilities, Requested Return on Equity, Percentage														9.525%												10.10%
Public Utilities, Rate Credit													$ 10.0
Potomac Electric Power Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												0.0
Accounts Payable, Current																																												84.0
Potomac Electric Power Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																								$ 13.0
Potomac Electric Power Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	3.0				3.0
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	301.0			314.0	301.0
Regulatory Liabilities																																	654.0			635.0	654.0
Revenues																																	328.0		327.0		1,001.0		971.0
Public Utilities, Requested Increase (Decrease), Amount	[1],[2]																																							14.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]																																							27.0
Public Utilities, Requested Return on Equity, Percentage																														10.10%
Prior Year Revenue Adjustment	[1],[2]																																							$ 13.0
Public Utilities, Approved Return on Equity, Percentage	[1],[2],[3]																																							10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2],[4]																																							7.29%
Public Utilities, Interim Rate Increase (Decrease), Amount																													$ 2.5
Payments to Acquire Property, Plant, and Equipment																																					254.0		294.0
Other Receivables																																	53.0			38.0	53.0
Accounts Payable, Current																																	104.0			82.0	104.0
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																				$ 7.0
Tax Savings From Tax Cuts and Jobs Act Through Effective Date		(1.0)
Public Utilities, Requested Increase (Decrease), Amount		$ (4.0)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																				4.0
Public Utilities, Requested Return on Equity, Percentage		9.70%
Public Utilities, Interim Rate Increase (Decrease), Amount																	$ 1.0
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																				19.0
Tax Savings From Tax Cuts and Jobs Act Through Effective Date								$ 3.0
Public Utilities, Requested Increase (Decrease), Amount								$ (7.0)																							$ 27.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																				12.0								$ 19.0
Public Utilities, Requested Return on Equity, Percentage								9.70%																							10.10%
Public Utilities, Approved Rate Increase (Decrease), Amount																											$ (13.0)
Public Utilities, Approved Return on Equity, Percentage																											9.50%
Public Utilities, Interim Rate Increase (Decrease), Amount																	$ 3.0
Delmarva Power and Light Company [Member] | Electric Distribution [Member] | Maryland Service Territory [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																				$ 13.0		31.0											14.0
Public Utilities, Rate Credit																																	2.0
Delmarva Power and Light Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												10.0
Accounts Payable, Current																																												0.0
Delmarva Power and Light Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																								$ 12.0
Delmarva Power and Light Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	5.0				5.0
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	427.0			430.0	427.0
Regulatory Liabilities																																	428.0			422.0	428.0
Tax Savings From Tax Cuts and Jobs Act																			$ 23.0
Revenues																																	406.0		$ 370.0		981.0		915.0
Public Utilities, Requested Increase (Decrease), Amount					$ 40.0				$ 40.0																															4.0	[1],[2]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1],[2]																																							0.0
Prior Year Revenue Adjustment	[1],[2]																																							$ (4.0)
Public Utilities, Approved Return on Equity, Percentage	[1],[2],[3]																																							10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2],[4]																																							8.02%
Payments to Acquire Property, Plant, and Equipment																																					247.0		$ 242.0
Other Receivables																																	59.0			56.0	59.0
Accounts Payable, Current																																	149.0			118.0	149.0
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act Through Effective Date			$ 6.0
Public Utilities, Requested Increase (Decrease), Amount					$ 109.0				$ 99.7
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																$ 13.0						$ 19.0
Public Utilities, Requested Return on Equity, Percentage					10.10%				10.10%
Public Utilities, Approved Rate Increase (Decrease), Amount												$ 33.0
Atlantic City Electric Company [Member] | PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Receivables																																												3.0
Accounts Payable, Current																																												0.0
Atlantic City Electric Company [Member] | Electric Transmission [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Tax Savings From Tax Cuts and Jobs Act																																								$ 11.0
Atlantic City Electric Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																																	1.0				1.0
Atlantic City Electric Company [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Payments to Acquire Property, Plant, and Equipment																																										$ 338.0
Zero Emission Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	18.0			112.0	18.0
Zero Emission Standard [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																																	61.0				315.0
Other Revenue, Net																																				150.0
Zero Emission Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	18.0			112.0	18.0
Zero Emission Standard [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	0.0			0.0	0.0
Zero Emission Standard [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	0.0			0.0	0.0
Zero Emission Standard [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	0.0			0.0	0.0
Zero Emission Standard [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	0.0			0.0	0.0
Zero Emission Standard [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	0.0			0.0	0.0
Zero Emission Standard [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	0.0			0.0	0.0
PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																												221.0
PJM Transmission Rate Design Settlement [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																												0.0
PJM Transmission Rate Design Settlement [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	101.0				101.0							122.0
PJM Transmission Rate Design Settlement [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	85.0				85.0							85.0
PJM Transmission Rate Design Settlement [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																												0.0
PJM Transmission Rate Design Settlement [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																												14.0
PJM Transmission Rate Design Settlement [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																												0.0
PJM Transmission Rate Design Settlement [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	10.0	[5]			10.0	[5]						10.0
PJM Transmission Rate Design Settlement [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																	3.0	[5]			3.0	[5]						4.0
Under Recovered Electric Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[6]																																1.0				1.0
Under-Recovered Natural Gas Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																				8.0
Pension and Other Postretirement Plans Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																3,710.0			3,848.0	3,710.0
Pension and Other Postretirement Plans Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			0.0	0.0
Pension and Other Postretirement Plans Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			0.0	0.0
Pension and Other Postretirement Plans Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			0.0	0.0
Pension and Other Postretirement Plans Costs [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			0.0	0.0
Pension and Other Postretirement Plans Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			0.0	0.0
Pension and Other Postretirement Plans Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			0.0	0.0
Pension and Other Postretirement Plans Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]																																0.0			$ 0.0	0.0
PJM Transmission Rate Design Settlement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												136.0
PJM Transmission Rate Design Settlement [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												0.0
PJM Transmission Rate Design Settlement [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												0.0
PJM Transmission Rate Design Settlement [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												0.0
PJM Transmission Rate Design Settlement [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	48.0				48.0							51.0
PJM Transmission Rate Design Settlement [Member] | Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												85.0
PJM Transmission Rate Design Settlement [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																	$ 74.0				$ 74.0							84.0
PJM Transmission Rate Design Settlement [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												0.0
PJM Transmission Rate Design Settlement [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																												$ 1.0

[1] All rates are effective June 2018, subject to review by the FERC and other parties, which is due by fourth quarter 2018.

[2] The initial revenue requirement changes reflect the annual benefit of lower income tax rates effective January 1, 2018 resulting from the enactment of the TCJA of $69 million, $18 million, $13 million, $12 million and $11 million for ComEd, BGE, Pepco, DPL and ACE, respectively. They do not reflect the pass back or recovery of income tax-related regulatory liabilities or assets, including those established upon enactment of the TCJA. See further discussion above.

[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% 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 regional transmission organization.

[4] Represents the weighted average debt and equity return on transmission rate bases.

[5] As of September 30, 2018, DPL's regulatory asset of $15 million included $14 million of transmission costs recoverable through its FERC approved formula rate and $1 million related to under-recovered electric energy costs. As of September 30, 2018, DPL's regulatory liability of $14 million included $10 million related to the PJM Transmission Rate Design Settlement and $4 million related to over-recovered electric energy and gas fuel costs. As of December 31, 2017, DPL's regulatory asset of $15 million included $8 million of transmission costs recoverable through its FERC approved formula rate and $7 million related to under-recovered electric energy costs. As of December 31, 2017, DPL's regulatory liability of $1 million related to over-recovered electric energy costs.

[6] As of September 30, 2018, ComEd’s regulatory asset of $7 million represents transmission costs recoverable through its FERC approved formula rate. As of September 30, 2018, ComEd’s regulatory liability of $204 million included $101 million related to the PJM Transmission Rate Design Settlement, $72 million related to over-recovered energy costs and $31 million associated with revenues received for renewable energy requirements. As of December 31, 2017, ComEd’s regulatory asset of $6 million represents transmission costs recoverable through its FERC approved formula rate. As of December 31, 2017, ComEd’s regulatory liability of $47 million included $14 million related to over-recovered energy costs and $33 million associated with revenues received for renewable energy requirements.

[7] Includes regulatory assets established at the Constellation and PHI merger dates of $401 million and $897 million, respectively, as of September 30, 2018 and $440 million and $953 million, respectively, as of December 31, 2017 related to the rate regulated portions of the deferred costs associated with legacy Constellation’s and PHI’s pension and other postretirement benefit plans that are being amortized and recovered over approximately 12 years and 3 to 15 years, respectively (as established at the respective acquisition dates). The Utility Registrants are not earning or paying a return on these amounts.