Commitments and Contingencies - Narrative (Details) $ in Millions		3 Months Ended		12 Months Ended
	Mar. 23, 2016 USD ($) MW	Mar. 31, 2020 USD ($) MGPSite Open_claim MW	Mar. 31, 2019 MW	Dec. 31, 2022 MW	Dec. 31, 2017 MW	Dec. 31, 2019 USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 2,718
Accrual for Environmental Loss Contingencies, Gross		472				$ 478
Liability for Asbestos and Environmental Claims, Gross		82				83
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		2,134
Accrual for Environmental Loss Contingencies, Gross		104				105
Liability for Asbestos and Environmental Claims, Gross		82				83
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 222
Mgp Site Contingency Monitoring Count | MGPSite		21
Accrual for Environmental Loss Contingencies, Gross		$ 301				304
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 187
Mgp Site Contingency Monitoring Count | MGPSite		8
Accrual for Environmental Loss Contingencies, Gross		$ 19				19
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 19
Mgp Site Contingency Monitoring Count | MGPSite		4
Accrual for Environmental Loss Contingencies, Gross		$ 2				2
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		48
Accrual for Environmental Loss Contingencies, Gross		46				48
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		23
Accrual for Environmental Loss Contingencies, Gross		44				46
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 15
Mgp Site Contingency 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		$ 27
Open Asbestos Related Personal Injury Claims | Open_claim		268
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		$ 55
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]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		280
West Lake [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		20
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	$ 127	$ 122
Other Non-Financial Commitment | MW		27
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		$ 122
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
Subsequent Event [Member] | Wind Assets [Member] | Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment | MW				40