Debt and Credit Agreements (Details) (USD $)	6 Months Ended												6 Months Ended					6 Months Ended									6 Months Ended															6 Months Ended														6 Months Ended
	Jun. 30, 2012	Jul. 18, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2012 Syndicated Revolver [Member]	Jun. 30, 2012 Bilateral Credit Facility [Member]	Jun. 30, 2012 Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 18, 2012 Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 30, 2012 Suboridanted Debentures [Member] Series A Junior Subordinated Debentures, 8.625% Due 2063 [Member]	Jun. 30, 2012 Exelon Corporate [Member] Commercial Paper [Member]	Dec. 31, 2011 Exelon Corporate [Member] Commercial Paper [Member]	Jun. 18, 2012 Exelon Corporate [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 30, 2012 Exelon Corporate [Member] Long Term Debt Retirements [Member] Senior Notes, 7.6% April 1,2032 [Member]	Jun. 30, 2012 Exelon Corporate [Member] Long Term Debt Retirements [Member] Medium Term Notes, 7.3% June 1,2012 [Member]	Mar. 31, 2012 Exelon Corporate [Member] Long Term Debt Assumed [Member] Senior Notes [Member]	Mar. 31, 2012 Exelon Corporate [Member] Long Term Debt Assumed [Member] Senior Notes [Member] Fixed Rate Debt [Member]	Jun. 28, 2012 Exelon Corporate [Member] Long Term Debt Exchange Offer Purchased [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] BasisPoints	Jul. 18, 2012 Exelon Generation Co L L C [Member]	Dec. 31, 2011 Exelon Generation Co L L C [Member]	Jun. 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]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Syndicated Revolver [Member]		Jun. 30, 2012 Exelon Generation Co L L C [Member] Bilateral Credit Facility [Member]		Jun. 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]	Jun. 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]	Jun. 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]	Jun. 30, 2011 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Armstrong Co Tax Exempt, 5% December 1,2042 [Member]	Jun. 18, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Issued And Sold [Member] Senior Notes [Member]	Jul. 13, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Purchased [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 28, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Purchased [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 28, 2012 Exelon Generation Co L L C [Member] Long Term Debt Exchange Offer Exchanged [Member] Senior Notes [Member]	Jun. 30, 2012 Commonwealth Edison Co [Member] BasisPoints	Dec. 31, 2011 Commonwealth Edison Co [Member]	Jun. 30, 2012 Commonwealth Edison Co [Member] Commercial Paper [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Commercial Paper [Member]	Jun. 30, 2012 Commonwealth Edison Co [Member] Syndicated Revolver [Member]		Jun. 30, 2011 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] First Mortgage Bonds, 1.625% January 15, 2014 [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] Sinking Fund Debentures, 4.75%, December 1, 2011 [Member]	Jun. 30, 2012 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds, 6.15% March 15, 2012 [Member]	Jul. 18, 2012 PECO Energy Co [Member]	Jun. 30, 2012 PECO Energy Co [Member]	Dec. 31, 2011 PECO Energy Co [Member]	Jun. 30, 2012 PECO Energy Co [Member] Commercial Paper [Member]	Dec. 31, 2011 PECO Energy Co [Member] Commercial Paper [Member]	Jun. 30, 2012 PECO Energy Co [Member] Syndicated Revolver [Member]		Jul. 18, 2012 Baltimore Gas and Electric Company [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member] Syndicated Revolver [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, 5.68% April 1, 2017 [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Medium Term, Notes 6.73% 6.75% June 15, 2012 [Member]
Credit Agreements [Abstract]
Additional amounts available upon request under current credit facilities																																				$ 500,000,000
Basis points adders for prime-based borrowings																																				65
Basis points adders for LIBOR-based borrowings																																				165
Basis Points For Cash Borrowings																																				35
Credit facility agreements with minority and community banks	118,000,000
Amount Of Aggregate Letters of Credit Available																																				500,000,000
Basis Points For Prime Based Borrowings Current																																				27.5
Basis Points For LIBOR Based Borrowings Current																																				127.5
Unamortized Debt Issuance Expense																																				3,000,000
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	296,000,000			329,000,000																																										296,000,000	329,000,000
AVSR Project Development Debt Agreement [Abstract]
Basis point spread on DOE loan advance																		37.5
DOE interest rate swap	485,000,000
DOE advances received																		69,000,000
DOE Interest Rate Swap Loan Advance																		52,000,000
Generation letters of credit outstanding to support project																		689,000,000
Long-Term Debt [Abstract]
Long-term debt	17,045,000,000		450,000,000	11,799,000,000												550,000,000		7,163,000,000		3,674,000,000																5,091,000,000	5,215,000,000									1,598,000,000	1,597,000,000						1,597,000,000	1,596,000,000
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								7.60%	8.625%				7.60%	7.30%	5.15%	4.55%											4.25%	5.60%	3.092%	7.83%	5.00%											1.625%	4.75%	6.15%												5.68%
Minimum interest rate on long-term debt																																																									6.73%
Maximum interest rate on long-term debt																																																									6.75%
Maturity date													April 1, 2032	June 1, 2012													June 15, 2022	June 15, 2042	January 2, 2037	September 20, 2020	December 1, 2042											January 15, 2014	December 1, 2011	March 15, 2012												April 1, 2017	June 15, 2012
Long Term Debt									450,000,000				441,000,000	2,000,000													523,000,000	787,000,000	69,000,000	1,000,000	46,000,000	775,000,000			535,000,000							600,000,000	1,000,000	450,000,000												31,000,000	110,000,000
Long term debt old notes							259,000,000					700,000,000					608,000,000																1,000,000	441,000,000
Cash payment related to exchange offer																																			60,000,000
Gain from exchange offer																																		13,000,000
Increase in fair value adjustment	403,000,000
Fair Value Adjustment Outstanding	224,000,000
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	10,700,000,000				2,000,000,000	900,000,000																	5,300,000,000	[1]	300,000,000	[1]														1,000,000,000	[1]									600,000,000	[1]				600,000,000
Footnotes To Line Of Credit Facility [Abstract]
Credit facility agreements with minority and community banks	118,000,000
Short Term Debt [Line Items]
Commercial paper borrowings	$ 0			$ 0						$ 188,000,000	$ 161,000,000										$ 0	$ 0																$ 178,000,000	$ 0									$ 0	$ 0

[1] Excludes $118 million of credit facility agreements arranged with minority and community banks at Generation, ComEd and PECO. These facilities, which expire in October 2012, are solely utilized to issue letters of credit.