Commitments and Contingencies - Narrative (Details)			12 Months Ended
	Oct. 30, 2020 USD ($)	Mar. 23, 2016 USD ($) MW	Dec. 31, 2022 MW	Dec. 31, 2020 USD ($) MGPSite Open_claim MW	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) MW	Dec. 31, 2017 MW	Sep. 30, 2020 USD ($)	Mar. 31, 2018 USD ($)
Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 71,000,000
Other Commitment				2,719,000,000
Accrual for Environmental Loss Contingencies, Gross				483,000,000	$ 478,000,000
Asbestos Liability Reserve				89,000,000	83,000,000
Contributions from parent					0	$ 0
West Lake [Member]
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross				280,000,000
Exelon Generation Co L L C [Member]
Commitments and Contingencies [Line Items]
Other Commitment				2,154,000,000
Nuclear financial protection pool value				450,000,000
Maximum recovery limit from a nuclear industry mutual insurance company in the event of multiple losses				13,300,000,000
Maximum annual assessment payment mandated by Price-Anderson Act for a nuclear incident				2,900,000,000
Mutual Insurance Total Retrospective Premium Obligation				252,000,000
Mutual Replacement Power Cost Insurance Maximum Retrospective Premium Obligation				3,200,000,000
Cost of spent nuclear fuel disposal per kWh of net nuclear generation				$ 0.001
Spent Nuclear Fuel Treasury Interest Rate				0.096%
Accrual for Environmental Loss Contingencies, Gross				$ 121,000,000	105,000,000
Asbestos Liability Reserve				89,000,000	83,000,000
Contributions from parent				$ 64,000,000	41,000,000	155,000,000
Spent Nuclear Fuel Treasury Interest Rate - FitzPatrick				0.101%
Exelon Generation Co L L C [Member] | West Lake [Member]
Commitments and Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross				$ 30,000,000
Environmental loss contingencies				90,000,000
Exelon Generation Co L L C [Member] | Nuclear Insurance Premiums [Member]
Commitments and Contingencies [Line Items]
Nuclear insurance liability limit per incident				13,800,000,000
Exelon Generation Co L L C [Member] | Nuclear Insurance Premiums [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Nuclear financial protection pool value				434,000,000
Exelon Generation Co L L C [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Commitments and Contingencies [Line Items]
Mutual Property Insurance Distribution To Members				75,000,000	136,000,000	58,000,000			$ 31,000,000
Commonwealth Edison Co [Member]
Commitments and Contingencies [Line Items]
Other Commitment				$ 223,000,000
Sites under study/remediation | MGPSite				21
Accrual for Environmental Loss Contingencies, Gross				$ 293,000,000	304,000,000
Estimated Litigation Liability, Current								$ 200,000,000
Estimated Litigation Liability, Current, Due within 30 days								100,000,000
Estimated Litigation Liability, Current, Due within 90 days								100,000,000
Contributions from parent				713,000,000	250,000,000	500,000,000
Commonwealth Edison Co [Member] | Deferred Prosecution Agreement Payments
Commitments and Contingencies [Line Items]
Estimated Litigation Liability, Current								$ 200,000,000
Contributions from parent	$ 200,000,000
Litigation Settlement, Amount Awarded to Other Party				200,000,000
PECO Energy Co [Member]
Commitments and Contingencies [Line Items]
Other Commitment				$ 180,000,000
Sites under study/remediation | MGPSite				8
Accrual for Environmental Loss Contingencies, Gross				$ 23,000,000	19,000,000
Contributions from parent				248,000,000	188,000,000	89,000,000
Baltimore Gas and Electric Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				$ 5,000,000
Sites under study/remediation | MGPSite				4
Accrual for Environmental Loss Contingencies, Gross				$ 2,000,000	2,000,000
Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio, Actual				0.48
Pepco Holdings LLC [Member]
Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 71,000,000
Other Commitment				50,000,000
Accrual for Environmental Loss Contingencies, Gross				44,000,000	48,000,000
Contributions from parent				494,000,000	398,000,000	385,000,000
Potomac Electric Power Company [Member]
Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				24,000,000
Other Commitment				23,000,000
Accrual for Environmental Loss Contingencies, Gross				$ 42,000,000	46,000,000
Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio, Actual				0.48
Contributions from parent				$ 262,000,000	160,000,000	166,000,000
Delmarva Power & Light Company [Member]
Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				30,000,000
Other Commitment				$ 16,000,000
Total number of MGP sites | MGPSite				1
Accrual for Environmental Loss Contingencies, Gross				$ 1,000,000	1,000,000
Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio, Actual				0.48
Contributions from parent				$ 112,000,000	63,000,000	150,000,000
Atlantic City Electric Company [Member]
Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				17,000,000
Other Commitment				11,000,000
Accrual for Environmental Loss Contingencies, Gross				$ 1,000,000	1,000,000
Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio, Actual				0.48
Contributions from parent				$ 117,000,000	$ 175,000,000	$ 67,000,000
Atlantic City Electric Company [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio, Actual				0.30
PEPCO Holdings Inc [Member]
Commitments and Contingencies [Line Items]
Other Commitment				$ 513,000,000
PEPCO Holdings Inc [Member] | Pepco Holdings LLC [Member]
Commitments and Contingencies [Line Items]
Other Commitment				320,000,000
PEPCO Holdings Inc [Member] | Potomac Electric Power Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				120,000,000
PEPCO Holdings Inc [Member] | Delmarva Power & Light Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				89,000,000
PEPCO Holdings Inc [Member] | Atlantic City Electric Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				$ 111,000,000
PEPCO Holdings Inc [Member] | Other Solar Projects [Member]
Commitments and Contingencies [Line Items]
Business Acquisition, Expected New Generation Mwh | MW		37		27
Other Commitment		$ 135,000,000		$ 119,000,000
PEPCO Holdings Inc [Member] | Other Solar Projects [Member] | Exelon Generation Co L L C [Member]
Commitments and Contingencies [Line Items]
Other Commitment				119,000,000
PEPCO Holdings Inc [Member] | Wind Assets [Member]
Commitments and Contingencies [Line Items]
OtherNonFinancialCommitment1 | MW		100
PEPCO Holdings Inc [Member] | Wind Assets [Member] | Delmarva Power & Light Company [Member]
Commitments and Contingencies [Line Items]
Purchase Commitment | MW		120				40	40
Subsequent Event [Member] | PEPCO Holdings Inc [Member] | Wind Assets [Member] | Delmarva Power & Light Company [Member]
Commitments and Contingencies [Line Items]
Purchase Commitment | MW			40
Open Claims [Member] | Exelon Generation Co L L C [Member]
Commitments and Contingencies [Line Items]
Asbestos Liability Reserve				$ 25,000,000
Open Asbestos Liability Claims | Open_claim				261
Estimated Future Claims [Member] | Exelon Generation Co L L C [Member]
Commitments and Contingencies [Line Items]
Asbestos Liability Reserve				$ 64,000,000
Remaining Commitment [Member] | PEPCO Holdings Inc [Member]
Commitments and Contingencies [Line Items]
Other Commitment				82,000,000
Remaining Commitment [Member] | PEPCO Holdings Inc [Member] | Pepco Holdings LLC [Member]
Commitments and Contingencies [Line Items]
Other Commitment				67,000,000
Remaining Commitment [Member] | PEPCO Holdings Inc [Member] | Potomac Electric Power Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				55,000,000
Remaining Commitment [Member] | PEPCO Holdings Inc [Member] | Delmarva Power & Light Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				7,000,000
Remaining Commitment [Member] | PEPCO Holdings Inc [Member] | Atlantic City Electric Company [Member]
Commitments and Contingencies [Line Items]
Other Commitment				$ 5,000,000