Regulatory Matters - Narrative (Details) - USD ($)			6 Months Ended
	Jul. 15, 2021	Feb. 15, 2021	Jun. 30, 2021	Jun. 15, 2021	Aug. 26, 2020
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			3,000,000,000.0
Market-wide Limit Recovery of Default			2,500,000
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]
Increase (Decrease) in Regulatory Assets			116,000,000
Commonwealth Edison Co [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			67,000,000
Commonwealth Edison Co [Member] | Energy Efficiency Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			85,000,000
Commonwealth Edison Co [Member] | Renewable energy swaps
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			36,000,000
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			95,000,000
Increase (Decrease) in Regulatory Liabilities			85,000,000
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			96,000,000
PECO Energy Co [Member] | Electric Energy and Natural Gas Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(13,000,000)
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			81,000,000
PECO Energy Co [Member] | Vacation Accrual
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			12,000,000
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			(109,000,000)
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(111,000,000)
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maryland Relief Act Funds				12,000,000
Increase (Decrease) in Regulatory Liabilities			(53,000,000)
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(46,000,000)
Potomac Electric Power Company [Member] | Electric Transmission Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(14,000,000)
Potomac Electric Power Company [Member] | District of Columbia 2019 Electric Distribution Base Rate Case [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			10,000,000
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			(32,000,000)
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(26,000,000)
Delmarva Power and Light Company [Member] | Electric Transmission Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(9,000,000)
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure					$ 220,000,000
Increase (Decrease) in Regulatory Liabilities			(27,000,000)
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(20,000,000)
Atlantic City Electric Company [Member] | Electric Transmission Formula Rate Annual Reconciliations [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			$ (6,000,000)