Debt and Credit Agreements (Details) (USD $)	9 Months Ended																9 Months Ended								3 Months Ended					9 Months Ended								9 Months Ended																																	9 Months Ended
	Sep. 30, 2012 BasisPoints	Aug. 10, 2012	Jul. 18, 2012	Dec. 31, 2011	Sep. 30, 2012 Syndicated Revolver [Member]	Sep. 30, 2012 Series A Junior Subordinated Debentures, 8.625% Due 2063 [Member]	Jun. 18, 2012 Senior Notes [Member]	Sep. 30, 2012 Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Sep. 30, 2012 Long Term Debt Retirements [Member] Medium Term Notes, 7.3% June 1,2012 [Member]	Sep. 30, 2012 Long Term Debt Retirements [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Sep. 30, 2012 Exelon Corporate [Member] BasisPoints	Sep. 30, 2012 Exelon Corporate [Member] Commercial Paper [Member]	Dec. 31, 2011 Exelon Corporate [Member] Commercial Paper [Member]	Sep. 30, 2012 Exelon Corporate [Member] Long Term Debt Assumed [Member] Senior Notes [Member]	Sep. 30, 2012 Exelon Corporate [Member] Long Term Debt Assumed [Member] Senior Notes [Member] Fixed Rate Debt [Member]	Sep. 30, 2012 Exelon Corporate [Member] Long Term Debt Exchange Offer Purchased [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] BasisPoints	Aug. 10, 2012 Exelon Generation Co L L C [Member]	Dec. 31, 2011 Exelon Generation Co L L C [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Commercial Paper [Member]	Dec. 31, 2011 Exelon Generation Co L L C [Member] Commercial Paper [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Syndicated Revolver [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Bilateral Credit Facility [Member]	Jul. 18, 2012 Exelon Generation Co L L C [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] DOE Financing Project [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] CEU Credit Agreement [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Clean Horizons [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] Senior Notes, 4.25% June 15, 2022 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] Senior Notes, 5.6% June 15, 2042 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member] DOE Project Financing, 3.092% January 2, 2037 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Sep. 30, 2011 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Armstrong Co Tax Exempt, 5% December 1,2042 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] CEU Credit Agreement [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] MEDCO Tax-Exempt Bonds [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Solar Revolver [Member]	Jun. 18, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Issued And Sold [Member] Senior Notes [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Purchased [Member]	Jul. 13, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Purchased [Member]	Jun. 28, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Purchased [Member]	Jun. 28, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Exchanged [Member] Senior Notes [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] BasisPoints	Dec. 31, 2011 Commonwealth Edison Co [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Commercial Paper [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Commercial Paper [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Syndicated Revolver [Member]	Sep. 30, 2011 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] First Mortgage Bonds, 1.625% January 15, 2014 [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] First Mortgage Bonds, 3.800% October 1, 2042 [Member]	Sep. 30, 2011 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] First Mortgage Bonds, 1.950% September 1, 2016 [Member]		Sep. 30, 2011 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] First Mortgage Bonds, 3.400% September 1, 2021 [Member]		Sep. 30, 2012 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] First Mortgage Bonds, 6.15% March 15, 2012 [Member]	Sep. 30, 2011 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] Sinking Fund Debentures [Member]	Sep. 30, 2011 Commonwealth Edison Co [Member] Proceeds From Issuance Of Debt [Member] First Mortgage Bonds [Member]	Sep. 30, 2012 PECO Energy Co [Member] BasisPoints	Aug. 10, 2012 PECO Energy Co [Member]	Dec. 31, 2011 PECO Energy Co [Member]	Sep. 30, 2012 PECO Energy Co [Member] Commercial Paper [Member]	Dec. 31, 2011 PECO Energy Co [Member] Commercial Paper [Member]	Sep. 30, 2012 PECO Energy Co [Member] Syndicated Revolver [Member]	Sep. 30, 2012 PECO Energy Co [Member] Long Term Debt Issuances [Member] First And Refunding Mortgage Bonds, 2.375% September 15, 2022 [Member]	Sep. 30, 2012 PECO Energy Co [Member] Long Term Debt Retirements [Member] First and Refunding Mortgage Bonds 4.750% October 1, 2012 [Member]	Sep. 30, 2012 PECO Energy Co [Member] Long Term Debt Retirements [Member] First and Refunding Mortgage Bonds 4.750% October 1, 2012 [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] BasisPoints	Aug. 10, 2012 Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Syndicated Revolver [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Issuances [Member] Ten Year Notes [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, 5.68% April 1, 2017 [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Medium Term, Notes 6.73% 6.75% June 15, 2012 [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Fixed Rate Debt [Member] Rate Stabilization Bonds, 5.68% April 1, 2017 [Member]
Credit Agreements [Abstract]
Additional amounts available upon request under current credit facilities											$ 250,000,000						$ 1,000,000,000																									$ 500,000,000														$ 250,000,000									$ 100,000,000
Basis points adders for prime-based borrowings	0.0065										0.00275						0.00075																																																0.00075
Basis points adders for LIBOR-based borrowings	0.0165										0.01275						0.01075																																							0.01									0.01075
Basis Points For Cash Borrowings																																										0.0035
Letters Of Credit											200,000,000						3,500,000,000																																							300,000,000									600,000,000
Amount Of Aggregate Letters of Credit Available																																										500,000,000
Previous Aggregate Commitments Of Acquired Entity	2,500,000,000
Amended Aggregate Commitments Of Acquired Entity	1,500,000,000
Aggregate bank commitments under amendment		500,000,000																5,300,000,000																																							600,000,000									600,000,000
Revolver Under Amendment			1,500,000,000
Accounts Receivable Agreement [Abstract]
Short-term notes payable - accounts receivable agreement	225,000,000			225,000,000																																																				225,000,000		225,000,000
Gross accounts receivable pledged as collateral	314,000,000			329,000,000																																																				314,000,000		329,000,000
AVSR Project Development Debt Agreement [Abstract]
Basis point spread on DOE loan advance	0.00375
DOE interest rate swap	485,000,000
DOE advances received																	69,000,000
DOE Interest Rate Swap Loan Advance																	100,000,000
Generation letters of credit outstanding to support project																	656,000,000
Long-Term Debt [Abstract]
Long-term debt	17,050,000,000			11,799,000,000		450,000,000	700,000,000		2,000,000	442,000,000					550,000,000		7,148,000,000		3,674,000,000							43,000,000	38,000,000			100,000,000	2,000,000	2,000,000	46,000,000	3,000,000	75,000,000	13,000,000			1,000,000	441,000,000		4,965,000,000	5,215,000,000				600,000,000	350,000,000	250,000,000	[1],[2]	350,000,000	[1],[2]	450,000,000	1,000,000		1,947,000,000		1,597,000,000				350,000,000			1,446,000,000		1,596,000,000		250,000,000	31,000,000	110,000,000	32,000,000
Long-term debt to financing trusts	649,000,000			390,000,000																																						206,000,000	206,000,000													184,000,000		184,000,000							258,000,000		258,000,000
Interest rate on long-term debt						8.625%			7.30%	7.60%				5.15%	4.55%									7.60%		1.99%	2.50%	4.25%	5.60%		7.83%	7.83%	5.00%	2.27%		2.49%											1.625%	3.80%	1.95%	[1],[2]	3.40%	[1],[2]	6.15%	4.75%	536000000.00%							2.375%	4.75%	225000000.00%					2.80%	5.68%
Minimum interest rate on long-term debt																									2.482%					2.33%																																									6.73%
Maximum interest rate on long-term debt																									2.595%					3.092%																																									6.75%
Long Term Debt																												523,000,000	788,000,000								775,000,000				535,000,000
Long term debt old notes								258,000,000								608,000,000
Cash payment related to exchange offer																																									60,000,000
DOE Advances received, $59 Million, October 1, 2012																									59,000,000
DOE Advances received, $2 Million, October 31, 2012																									2,000,000
Increase in fair value adjustment	403,000,000																																					13,000,000
Fair Value Adjustment Outstanding	212,000,000
Footnotes To Long-Term Debt [Abstract]
Notional amount of interest rate cash flow hedge derivatives																																					470,000,000
Loss on interest rate swap																																					7,000,000
Line Of Credit Facility [Abstract]
Aggregate bank commitments under unsecured revolving credit facilities	9,800,000,000				2,000,000,000																	5,300,000,000	300,000,000																							1,000,000,000															600,000,000							600,000,000
Outstanding letters of credit											200,000,000						3,500,000,000																																							300,000,000									600,000,000
Footnotes To Line Of Credit Facility [Abstract]
Credit facility agreements with minority and community banks	118,000,000																50,000,000																									34,000,000														34,000,000									5,000,000
Short Term Debt [Line Items]
Commercial paper borrowings	$ 0			$ 0								$ 15,000,000	$ 161,000,000							$ 0	$ 0																							$ 35,000,000	$ 0														$ 0	$ 0

[1] As of September 30, 2011, $536 million of the total proceeds from the issuances of First Mortgage Bonds due September 1, 2016 and September 1, 2021 was reflected in restricted cash on Exelon’s and ComEd’s Consolidated Balance Sheets for the purpose of redeeming outstanding debt under ComEd’s long-term debt refinancing authority with the ICC.

[2] To be used to refinance the outstanding principal amount of three series of variable rate tax-exempt bonds, to refinance the outstanding principal of First Mortgage 5.40% Bonds due December 15, 2011.