Regulatory Matters - Narrative (Details)				9 Months Ended
	Sep. 23, 2021 USD ($)	Jul. 15, 2021	Feb. 15, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jul. 09, 2021 USD ($)	Jul. 02, 2021 USD ($)	Aug. 26, 2020 USD ($)
Texas-based generating assets
Regulatory Matters Additional Narrative Information [Line Items]
Operating and maintenance				$ 880,000,000
Market Payment Shortfall in Collections				17,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Return on Equity, Percentage		9.33%
Exelon Generation Co L L C [Member] | ERCOT
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 9,000
Market Payment Shortfall in Collections				3,000,000,000
Market-wide Limit Recovery of Default				2,500,000
Securitized Funds Allocation				2,100,000,000
System-Wide Offer Cap	$ 4,500
Exelon Generation Co L L C [Member] | Texas-based generating assets
Regulatory Matters Additional Narrative Information [Line Items]
Operating and maintenance				880,000,000
Market Payment Shortfall in Collections				$ 17,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Carbon mitigation credit				54,500,000
Maximum increase of revenue requirement				5.00%
Increase (Decrease) in Regulatory Assets				$ 93,000,000
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Basis points for ComEd's Electric Distribution rates				20
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Basis points for ComEd's Electric Distribution rates				60
Commonwealth Edison Co [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				$ 47,000,000
Commonwealth Edison Co [Member] | Energy Efficiency Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				127,000,000
Commonwealth Edison Co [Member] | Renewable energy swaps
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				(87,000,000)
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				135,000,000
Increase (Decrease) in Regulatory Liabilities				66,000,000
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				71,000,000
PECO Energy Co [Member] | Electric Energy and Natural Gas Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(18,000,000)
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				123,000,000
PECO Energy Co [Member] | Vacation Accrual
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets				14,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds						$ 50,000,000
Increase (Decrease) in Regulatory Liabilities				(116,000,000)
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(128,000,000)
Baltimore Gas and Electric Company [Member] | Other [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				12,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds						$ 12,000,000
Increase (Decrease) in Regulatory Liabilities				(108,000,000)
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(89,000,000)
Potomac Electric Power Company [Member] | Electric Transmission Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(19,000,000)
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds					$ 8,000,000
Increase (Decrease) in Regulatory Liabilities				(45,000,000)
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(41,000,000)
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure							$ 220,000,000
Increase (Decrease) in Regulatory Liabilities				(61,000,000)
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				(67,000,000)
Atlantic City Electric Company [Member] | Stranded Costs
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities				$ 14,000,000