Debt and Credit Agreements (Details) (USD $)	3 Months Ended															3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Syndicated Revolver [Member]	Mar. 31, 2013 Exelon Corporate [Member]	Mar. 31, 2013 Exelon Corporate [Member] Commercial Paper [Member]	Dec. 31, 2012 Exelon Corporate [Member] Commercial Paper [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member]	Jan. 23, 2013 Exelon Generation Co L L C [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member] Commercial Paper [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member] Commercial Paper [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member] Syndicated Revolver [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member] Bilateral Credit Facility [Member]	Jan. 23, 2013 Exelon Generation Co L L C [Member] Bilateral Credit Facility [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] Senior Notes, 4.25% June 15, 2022 [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member]	Mar. 31, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] First Mortgage Bond Series 98, 7.6% April 1, 2032 [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Mar. 31, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Capital Lease Obligations [Member]	Mar. 31, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Mar. 31, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]	Mar. 31, 2013 Commonwealth Edison Co [Member] Commercial Paper [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Commercial Paper [Member]	Mar. 31, 2013 Commonwealth Edison Co [Member] Syndicated Revolver [Member]	Apr. 15, 2013 Commonwealth Edison Co [Member] First Mortgage Bonds [Member] Repayment of Debt [Member]	Mar. 31, 2013 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]	Mar. 31, 2013 PECO Energy Co [Member] Commercial Paper [Member]	Dec. 31, 2012 PECO Energy Co [Member] Commercial Paper [Member]	Mar. 31, 2013 PECO Energy Co [Member] Syndicated Revolver [Member]	Mar. 31, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]	Mar. 31, 2013 Baltimore Gas and Electric Company [Member] Syndicated Revolver [Member]
Credit Agreements [Abstract]
Additional amounts available upon request under current credit facilities																					$ 500,000,000
Basis points adders for prime-based borrowings	0.0065			0.275			0.275														0.275											0.075
Basis points adders for LIBOR-based borrowings	0.0165			1.275			1.275														1.275						1					1.075
Bilateral letters of credit								75,000,000
Amount Of Aggregate Letters of Credit Available																					500,000,000
Accounts Receivable Agreement [Abstract]
Short-term notes payable - accounts receivable agreement	210,000,000	210,000,000																									210,000,000	210,000,000
Gross accounts receivable pledged as collateral	322,000,000	289,000,000																									322,000,000	289,000,000
AVSR Project Development Debt Agreement [Abstract]
DOE interest rate swap	485,000,000
Long-Term Debt [Abstract]
Long-term debt to affiliate							1,997,000,000		2,007,000,000
Long-term debt	16,210,000,000	17,190,000,000					4,893,000,000		5,245,000,000								450,000,000	1,000,000	1,000,000		4,699,000,000	5,315,000,000				125,000,000	1,648,000,000	1,647,000,000				1,446,000,000	1,446,000,000
Long-term debt to financing trusts	648,000,000	648,000,000																			206,000,000	206,000,000					184,000,000	184,000,000				258,000,000	258,000,000
Interest rate on long-term debt															2.21%		6.15%	7.83%		7.83%						7.625%
Minimum interest rate on long-term debt																2.72%
Maximum interest rate on long-term debt																2.81%
Long Term Debt															3,000,000	146,000,000
Line Of Credit Facility [Abstract]
Aggregate bank commitments under unsecured revolving credit facilities	8,400,000,000		500,000,000									5,300,000,000	300,000,000	100,000,000											1,000,000,000						600,000,000			600,000,000
Footnotes To Line Of Credit Facility [Abstract]
Credit facility agreements with minority and community banks							50,000,000														34,000,000						34,000,000					5,000,000
Letters of credit							25,000,000														26,000,000						21,000,000					1,000,000
Short Term Debt [Line Items]
Commercial paper borrowings	$ 0	$ 0			$ 0	$ 0				$ 0	$ 0												$ 220,000,000	$ 0					$ 0	$ 0