Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	$ 354	$ 352
Commonwealth Edison Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	279	279
PECO Energy Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	21	22
Baltimore Gas and Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	7	6
Pepco Holdings LLC [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	42	42
Potomac Electric Power Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	40	40
Delmarva Power and Light Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	1	1
Atlantic City Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	1	1
Accrual For MGP Investigation And Remediation [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	305	303
Accrual For MGP Investigation And Remediation [Member] | Commonwealth Edison Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	279	279
Accrual For MGP Investigation And Remediation [Member] | PECO Energy Co [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	20	20
Accrual For MGP Investigation And Remediation [Member] | Baltimore Gas and Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	6	4
Accrual For MGP Investigation And Remediation [Member] | Pepco Holdings LLC [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Potomac Electric Power Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Delmarva Power and Light Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Atlantic City Electric Company [Member]
Site Contingency [Line Items]
Total environmental investigation and remediation reserve	$ 0	$ 0