Regulatory Matters - Narrative (Details)				1 Months Ended			3 Months Ended			6 Months Ended			12 Months Ended
		Jun. 03, 2016 USD ($)	Apr. 30, 2012 MW	Aug. 31, 2014 USD ($)	May 31, 2014 USD ($)	Mar. 31, 2013 USD ($)	Jun. 30, 2016 USD ($)		Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)		Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)		Jul. 31, 2014 USD ($)	Aug. 31, 2010 USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							$ 11,680,000,000			$ 11,680,000,000			$ 6,824,000,000
Business Combination, Integration Related Costs							1,000,000		$ (87,000,000)	103,000,000		$ 21,000,000
Capital Expenditures Incurred but Not yet Paid										(364,000,000)
Regulatory Liabilities							4,892,000,000			4,892,000,000			4,570,000,000
Regulatory assets							10,121,000,000			10,121,000,000			6,065,000,000
Regulatory Liability, Current							503,000,000			503,000,000			369,000,000
Other Commitment							6,399,000,000			6,399,000,000
Fair Value, Net Asset (Liability)							2,400,000,000			2,400,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							1,136,000,000			1,136,000,000			1,113,000,000
Business Combination, Integration Related Costs							1,000,000		3,000,000	(7,000,000)		$ 6,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										94,000,000
Capital Expenditures Incurred but Not yet Paid										(21,000,000)
Regulatory Liabilities							3,677,000,000			3,677,000,000			3,614,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount										$ 90,000,000
Approved ROE										11.50%
Public Utilities, Requested Rate Increase (Decrease), Percentage										8.64%		8.59%
Regulatory assets							923,000,000			$ 923,000,000			895,000,000
Regulatory Liability, Current							153,000,000			153,000,000			155,000,000
Other Commitment							226,000,000			226,000,000
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										138,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount										139,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount										$ 1,000,000
Requested Debt and Equity Return on Distribution										6.71%		6.69%
ICC Approved Rate Increase (Decrease), Amount										$ 1,000,000
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							1,684,000,000			1,684,000,000			1,617,000,000
Business Combination, Integration Related Costs							1,000,000		1,000,000	2,000,000		$ 2,000,000
Capital Expenditures Incurred but Not yet Paid										(12,000,000)
Regulatory Liabilities							657,000,000			657,000,000			639,000,000
Regulatory assets							1,636,000,000			1,636,000,000			1,583,000,000
Regulatory Liability, Current							128,000,000			128,000,000			112,000,000
Other Commitment							210,000,000			210,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							781,000,000			781,000,000			781,000,000
Business Combination, Integration Related Costs							(5,000,000)		1,000,000	(4,000,000)		3,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										15,000,000
Customer Refund Liability, Noncurrent							30,000,000			30,000,000
Capital Expenditures Incurred but Not yet Paid										2,000,000
Regulatory Liabilities							197,000,000			197,000,000			222,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount										12,000,000
Estimated number of smart meters to be installed																2,000,000
Total smart grid and smart meter investment grant amount																$ 480,000,000
Reimbursements received from the DOE																$ 200,000,000
Regulatory assets							520,000,000			520,000,000			514,000,000
Customer Refund							30,000,000			$ 30,000,000
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint										10.50%
Regulatory Liability, Current							60,000,000			$ 60,000,000			38,000,000
Other Commitment							262,000,000			262,000,000
Proposed Capital Expenditure										13,000,000
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 48,000,000								78,000,000
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										116,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount		44,000,000
ICC Approved Rate Increase (Decrease), Amount		$ 44,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Business Combination, Integration Related Costs							4,000,000		7,000,000	20,000,000		15,000,000
Unregulated Operating Revenue										101,000,000
Customer Refund Liability, Noncurrent							20,000,000			20,000,000
Capital Expenditures Incurred but Not yet Paid										(317,000,000)
Customer Refund							20,000,000			20,000,000
License Costs										26,000,000
Other Commitment							5,589,000,000			5,589,000,000					$ 91,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation							3,000,000			3,000,000
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation							7,000,000			7,000,000
PEPCO Holdings Inc [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment							37,000,000			37,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							798,000,000			798,000,000			801,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										(23,000,000)
Capital Expenditures Incurred but Not yet Paid										11,000,000
Regulatory Liabilities							$ 51,000,000			51,000,000			44,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount										2,000,000
Approved ROE							10.60%
Regulatory assets							$ 669,000,000			$ 669,000,000			661,000,000
Public Utilities, Requested Return on Equity, Percentage										10.60%
Power Plant Output | MW			661,000,000
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint										10.50%
CapitalProjectFundedByEntity					$ 500,000,000
Capital ProjectFundedByBonds					375,000,000
CapitalProjectFundedByAgency					125,000,000
Regulatory Liability, Current							27,000,000			$ 27,000,000			15,000,000
Other Commitment							14,000,000			14,000,000
Projected Capital Expenditures					$ 1,000,000,000
Current Year Revenue Adjustment										$ (15,000,000)
Requested ROE										10.60%
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount							127,000,000			$ 86,000,000
Potomac Electric Power Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Power Plant Output | MW			650,000,000
Proposed Capital Expenditure										16,000,000
Potomac Electric Power Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Power Plant Output | MW			700,000,000
Projected Capital Expenditures										32,000,000
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							358,000,000			358,000,000			371,000,000
Business Combination, Integration Related Costs							0		1,000,000	16,000,000		1,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										(14,000,000)
Capital Expenditures Incurred but Not yet Paid										(9,000,000)
Regulatory Liabilities							155,000,000			155,000,000			160,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount							62,800,000			$ 8,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 15,000,000
Requested Debt and Equity Return on Distribution										10.60%
Public Utilities, Interim Rate Increase (Decrease), Amount										$ 2,500,000
Approved ROE				9.70%
ICC Approved Rate Increase (Decrease), Amount				$ 15,000,000
Regulatory assets							295,000,000			$ 295,000,000			299,000,000
Public Utilities, Requested Return on Equity, Percentage										10.60%
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint										10.50%
Regulatory Liability, Current							53,000,000			$ 53,000,000			49,000,000
Other Commitment							11,000,000			11,000,000
Current Year Revenue Adjustment										$ (12,000,000)
Requested ROE										10.60%
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount										$ 21,500,000
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 42,000,000				66,000,000
Delmarva Power and Light Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected Capital Expenditures										5,000,000
Delmarva Power and Light Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected Capital Expenditures										9,000,000
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							515,000,000			515,000,000			512,000,000
Business Combination, Integration Related Costs							2,000,000		$ 1,000,000	15,000,000		$ 1,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										(6,000,000)
Capital Expenditures Incurred but Not yet Paid										6,000,000
Regulatory Liabilities							23,000,000			23,000,000			25,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount										8,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount							9,000,000			19,000,000
Regulatory assets							418,000,000			$ 418,000,000			414,000,000
Public Utilities, Requested Return on Equity, Percentage										10.60%
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint										10.50%
Regulatory Liability, Current							21,000,000			$ 21,000,000			18,000,000
Other Commitment							9,000,000			9,000,000
Current Year Revenue Adjustment										0
Proposed Capital Expenditure										$ 176,000,000
Requested ROE										10.60%
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount										$ 85,000,000
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							103,000,000			103,000,000			84,000,000
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[1]						41,000,000			41,000,000			43,000,000
Business Combination, Integration Related Costs										7,000,000			7,000,000
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			1,000,000	[2]
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[3]						36,000,000			36,000,000			40,000,000
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			9,000,000	[4]
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[5]						6,000,000			6,000,000			11,000,000
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[6]						20,000,000			20,000,000			13,000,000
Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							23,000,000			23,000,000			6,000,000
Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets
Merger Integration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			0
Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]						11,000,000			11,000,000			6,000,000
Merger Integration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							9,000,000	[8]		9,000,000	[8]		0
Merger Integration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							3,000,000	[9]		3,000,000	[9]		0
Merger Integration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			0
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							207,000,000			207,000,000			189,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[10]						207,000,000			207,000,000			189,000,000
Business Combination, Integration Related Costs										11,000,000			11,000,000
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			0
Under Recovered Distribution Service Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			0
Under Recovered Distribution Service Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0
Under Recovered Distribution Service Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0
Under Recovered Distribution Service Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							712,000,000			712,000,000			399,000,000
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													140,000,000
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													63,000,000
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[11]												196,000,000
Regulatory assets							240,000,000			240,000,000			196,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets							52,000,000			52,000,000
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										37,000,000
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										104,000,000
AMI Expenses [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							174,000,000	[11]		174,000,000	[11]		180,000,000
AMI Expenses [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							86,000,000	[11]		86,000,000	[11]		87,000,000
AMI Expenses [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			0
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							634,000,000			634,000,000			279,000,000
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			0
Energy Efficiency And Demand Response Programs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							1,000,000			1,000,000			1,000,000
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							264,000,000			264,000,000			278,000,000
Energy Efficiency And Demand Response Programs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							266,000,000			266,000,000			289,000,000
Energy Efficiency And Demand Response Programs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							103,000,000			103,000,000			111,000,000
Energy Efficiency And Demand Response Programs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0			0			$ 1,000,000
Legacy AMI [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							56,000,000			56,000,000
Legacy AMI [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							78,000,000			78,000,000
Legacy AMI [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							$ 14,000,000			$ 14,000,000

[1] As of June 30, 2016, ComEd’s regulatory asset of $41 million included $4 million related to under-recovered energy costs, $30 million associated with transmission costs recoverable through its FERC approved formula rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2016, ComEd’s regulatory liability of $41 million included $13 million related to over-recovered energy costs and $28 million associated with revenues received for renewable energy requirements. As of December 31, 2015, ComEd’s regulatory asset of $43 million included $5 million related to under-recovered energy costs, $31 million associated with transmission costs recoverable through its FERC approved formula rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2015, ComEd’s regulatory liability of $53 million included $29 million related to over-recovered energy costs and $24 million associated with revenues received for renewable energy requirements.

[2] As of June 30, 2016, PECO's regulatory liability of $63 million included $31 million related to over-recovered costs under the DSP program, $23 million related to the over-recovered natural gas costs under the PGC, $7 million related to over-recovered non-bypassable transmission service charges and$2 million related to over-recovered electric transmission costs. As of December 31, 2015, PECO's regulatory asset of $1 million related to under-recovered non-bypassable transmission service charges. As of December 31, 2015, PECO's regulatory liability of $60 million included $35 million related to over-recovered costs under the DSP program, $22 million related to the over-recovered natural gas costs under the PGC and $3 million related to the over-recovered electric transmission costs.

[3] As of June 30, 2016, BGE's regulatory asset of $36 million included $6 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $29 million related to under-recovered electric energy costs, and $1 million of abandonment costs to be recovered upon FERC approval. As of June 30, 2016, BGE's regulatory liability of $8 million related to $8 million of over-recovered natural gas costs. As of December 31, 2015, BGE’s regulatory asset of $40 million included $12 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $28 million related to under-recovered electric energy costs. As of December 31, 2015, BGE’s regulatory liability of $18 million related to $14 million of over-recovered transmission costs and $5 million of over-recovered natural gas costs, offset by $1 million of abandonment costs to be recovered upon FERC approval.

[4] As of June 30, 2016, Pepco's regulatory liability of $22 million included $12 million of over-recovered transmission costs and $10 million of over-recovered electric energy costs. As of December 31, 2015, Pepco's regulatory asset of $9 million included $5 million of transmission costs recoverable through its FERC approved formula rate and $4 million of recoverable abandonment costs. As of December 31, 2015, Pepco's regulatory liability of $16 million included $14 million of over-recovered transmission costs and $2 million of over-recovered electric energy costs.

[5] As of June 30, 2016, DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2016, DPL's regulatory liability of $21 million included $4 million related to over-recovered natural gas costs under the GCR mechanism, $10 million of over-recovered electric energy costs, and $7 million of over-recovered transmission costs. As of December 31, 2015, DPL's regulatory asset of $11 million included $7 million of transmission costs recoverable through its FERC approved formula rate, $3 million of recoverable abandonment costs, and $1 million of under-recovered electric energy costs. As of December 31, 2015, DPL's regulatory liability of $19 million included $4 million related to the over-recovered natural gas costs under the GCR mechanism, $4 million of over-recovered electric energy costs, and $11 million of over-recovered transmission costs.

[6] As of June 30, 2016, ACE's regulatory asset of $20 million related to of under-recovered electric energy costs. As of June 30, 2016, ACE's regulatory liability of $9 million related to over-recovered transmission costs. As of December 31, 2015, ACE's regulatory asset of $13 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2015, ACE's regulatory liability of $8 million related to over-recovered transmission costs.

[7] As of June 30, 2016, BGE's regulatory asset of $11 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.

[8] epresents previously incurred PHI acquisition costs expected to be recovered in distribution rates

[9] .

[10] As of June 30, 2016, ComEd’s regulatory asset of $207 million was comprised of $163 million for the 2014 - 2016 annual reconciliations and $44 million related to significant one-time events including $28 million of deferred storm costs, $11 million of Constellation and PHI merger and integration related costs and $5 million of smart meter related costs. As of December 31, 2015, ComEd’s regulatory asset of $189 million was comprised of $142 million for the 2014 and 2015 annual reconciliations and $47 million related to significant one-time events, including $36 million of deferred storm costs and $11 million of Constellation merger and integration related costs. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2015 Form 10-K for further information.

[11] $139 million for Pepco and $43 million for DPL, of which $78 million for Pepco and $14 million for DPL relates to retired legacy meters which are not earning a return