Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Jan. 31, 2021	Jun. 30, 2020
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-16169
Entity Registrant Name	EXELON CORPORATION
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-2990190
Entity Address, Address Line One	10 South Dearborn Street
Entity Address, Address Line Two	P.O. Box 805379
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60680-5379
City Area Code	(800)
Local Phone Number	483-3220
Title of 12(b) Security	Common Stock, without par value
Trading Symbol	EXC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 35,402,501,369
Entity Common Stock Shares Outstanding		976,337,799
Documents Incorporated by Reference [Text Block]	Portions of the Exelon Proxy Statement for the 2020 Annual Meeting of Shareholders and the Commonwealth Edison Company 2020 Information Statement are incorporated by reference in Part III.
Entity Central Index Key	0001109357
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Exelon Generation Co L L C [Member]
Entity File Number	333-85496
Entity Registrant Name	EXELON GENERATION COMPANY, LLC
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-3064219
Entity Address, Address Line One	300 Exelon Way
Entity Address, City or Town	Kennett Square
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19348-2473
City Area Code	(610)
Local Phone Number	765-5959
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001168165
Commonwealth Edison Co [Member]
Entity File Number	001-01839
Entity Registrant Name	COMMONWEALTH EDISON COMPANY
Entity Incorporation, State or Country Code	IL
Entity Tax Identification Number	36-0938600
Entity Address, Address Line One	440 South LaSalle Street
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60605-1028
City Area Code	(312)
Local Phone Number	394-4321
Title of 12(g) Security	Common Stock Purchase Warrants (1971 Warrants and Series B Warrants)
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		127,021,370
Entity Central Index Key	0000022606
PECO Energy Co [Member]
Entity File Number	000-16844
Entity Registrant Name	PECO ENERGY COMPANY
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-0970240
Entity Address, Address Line One	P.O. Box 8699
Entity Address, Address Line Two	2301 Market Street
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19101-8699
City Area Code	(215)
Local Phone Number	841-4000
Title of 12(b) Security	Cumulative Preferred Security, Series D,
Trading Symbol	EXC/28
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		170,478,507
Entity Central Index Key	0000078100
Baltimore Gas and Electric Company [Member]
Entity File Number	001-01910
Entity Registrant Name	BALTIMORE GAS AND ELECTRIC COMPANY
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	52-0280210
Entity Address, Address Line One	2 Center Plaza
Entity Address, Address Line Two	110 West Fayette Street
Entity Address, City or Town	Baltimore
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21201-3708
City Area Code	(410)
Local Phone Number	234-5000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		1,000
Entity Central Index Key	0000009466
Pepco Holdings LLC [Member]
Entity File Number	001-31403
Entity Registrant Name	PEPCO HOLDINGS LLC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2297449
Entity Address, Address Line One	701 Ninth Street, N.W.
Entity Address, City or Town	Washington, District of Columbia
Entity Address, Postal Zip Code	20068
City Area Code	(202)
Local Phone Number	872-2000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001135971
Potomac Electric Power Company [Member]
Entity File Number	001-01072
Entity Registrant Name	POTOMAC ELECTRIC POWER COMPANY
Entity Tax Identification Number	53-0127880
Entity Address, Address Line One	701 Ninth Street, N.W.
Entity Address, City or Town	Washington, District of Columbia
Entity Address, Postal Zip Code	20068
City Area Code	(202)
Local Phone Number	872-2000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		100
Entity Central Index Key	0000079732
Delmarva Power & Light Company [Member]
Entity File Number	001-01405
Entity Registrant Name	DELMARVA POWER & LIGHT COMPANY
Entity Tax Identification Number	51-0084283
Entity Address, Address Line One	500 North Wakefield Drive
Entity Address, City or Town	Newark
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19702
City Area Code	(202)
Local Phone Number	872-2000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		1,000
Entity Central Index Key	0000027879
Atlantic City Electric Company [Member]
Entity File Number	001-03559
Entity Registrant Name	ATLANTIC CITY ELECTRIC COMPANY
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	21-0398280
Entity Address, Address Line One	500 North Wakefield Drive
Entity Address, City or Town	Newark
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19702
City Area Code	(202)
Local Phone Number	872-2000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding		8,546,017
Entity Central Index Key	0000008192
VIRGINIA | Potomac Electric Power Company [Member]
Entity Incorporation, State or Country Code	VA
VIRGINIA | Delmarva Power & Light Company [Member]
Entity Incorporation, State or Country Code	VA
DELAWARE | Delmarva Power & Light Company [Member]
Entity Incorporation, State or Country Code	DE
DISTRICT OF COLUMBIA | Potomac Electric Power Company [Member]
Entity Incorporation, State or Country Code	DC