Commitments and Contingencies - Narrative (Details) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016 USD ($) MW	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) Open_claim MGPSite MW	Dec. 31, 2022 MW	Dec. 31, 2018 MW	Dec. 31, 2017 MW	Mar. 31, 2021 USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 3,621
Accrual for Environmental Loss Contingencies, Gross		$ 483	474
Liability for Asbestos and Environmental Claims, Gross		89	82
LDC Damages - Accrued Liability
Commitments And Contingencies Additional Narrative Information [Line Items]
LDC Damages			40
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			3,049
Accrual for Environmental Loss Contingencies, Gross		121	119
Liability for Asbestos and Environmental Claims, Gross		89	82
Exelon Generation Co L L C [Member] | LDC Damages
Commitments And Contingencies Additional Narrative Information [Line Items]
LDC Damages							$ 40
Exelon Generation Co L L C [Member] | LDC Damages - Accrued Liability
Commitments And Contingencies Additional Narrative Information [Line Items]
LDC Damages			40
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 224
Mgp Site Contingency Monitoring Count | MGPSite			21
Accrual for Environmental Loss Contingencies, Gross		293	$ 284
Deferred Prosecution Agreement Payments		200
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 181
Mgp Site Contingency Monitoring Count | MGPSite			6
Accrual for Environmental Loss Contingencies, Gross		23	$ 23
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 5
Mgp Site Contingency Monitoring Count | MGPSite			4
Accrual for Environmental Loss Contingencies, Gross		2	$ 6
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			54
Accrual for Environmental Loss Contingencies, Gross		44	42
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			24
Accrual for Environmental Loss Contingencies, Gross		42	40
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 18
Mgp Site Contingency Monitoring Count | MGPSite			1
Accrual for Environmental Loss Contingencies, Gross		$ 1	$ 1
Open Claims [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Liability for Asbestos and Environmental Claims, Gross			$ 19
Open Asbestos Related Personal Injury Claims | Open_claim			211
Estimated Future Claims [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Liability for Asbestos and Environmental Claims, Gross			$ 63
Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			513
Pepco Holdings Inc [Member] | Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			320
Pepco Holdings Inc [Member] | Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			120
Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			89
West Lake [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross			290
West Lake [Member] | Exelon Generation Co L L C [Member] | Groundwater
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross			40
West Lake [Member] | Exelon Generation Co L L C [Member] | Radioactive Residues Environmental Remediation
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Component Amount			90
Other Solar Projects [Member] | Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Business Acquisition, Expected New Generation Mwh | MW	37
Other Commitment	$ 135		$ 121
Other Non-Financial Commitment | MW			33
Other Solar Projects [Member] | Pepco Holdings Inc [Member] | Generation Solar Business
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Non-Financial Commitment | MW			30
Other Solar Projects [Member] | Pepco Holdings Inc [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment			$ 121
Wind Assets [Member] | Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Non-Financial Commitment | MW	100
Wind Assets [Member] | Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment | MW	120			40	40	40