Debt and Credit Agreements (Details) (USD $)					9 Months Ended		3 Months Ended	9 Months Ended						9 Months Ended															9 Months Ended					9 Months Ended												9 Months Ended		9 Months Ended																																	9 Months Ended
	Sep. 30, 2013	Aug. 10, 2013	Dec. 31, 2012	Sep. 30, 2013 Syndicated Revolver [Member]	Sep. 30, 2013 Debt Continental Project [Member] MW	Sep. 30, 2012 Fair Value Hedging [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Fair Value Hedging [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Fair Value Hedging [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Rate Swap [Member] Fair Value Hedging [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Interest Rate Swap [Member] Fair Value Hedging [Member]	Sep. 30, 2013 Exelon Corporate [Member]	Sep. 30, 2012 Exelon Corporate [Member] Long Term Debt Retirements [Member] Medium Term Notes, 7.3% June 1,2012 [Member]	Sep. 30, 2012 Exelon Corporate [Member] Long Term Debt Retirements [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member]	Aug. 10, 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]	Oct. 18, 2013 Exelon Generation Co L L C [Member] SubsequentEventTypeMember [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Syndicated Revolver [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member] Syndicated Revolver [Member] Continetal Wind [Member]	Sep. 30, 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]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Letter of Credit [Member] Continetal Wind [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Designated as Hedging Instrument [Member] Foreign Exchange Contract [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Designated as Hedging Instrument [Member] Interest Rate Swap [Member] Debt Continental Project [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] CEU Credit Agreement [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Upstream Gas Property [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] Fixed Rate Debt [Member] Senior Notes, 4.25% June 15, 2022 [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member] Senior Notes, 5.6% June 15, 2042 [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] Fixed Rate Debt [Member] Continental Wind 6000 February 28, 2033 [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Energy Efficiency Project Financing [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] First Mortgage Bond Series 98, 7.6% April 1, 2032 [Member]	Sep. 30, 2013 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] Upstream Gas Property [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Clean Horizons [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] Capital Lease Obligations [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Suboridanted Debentures [Member]		Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Solar Revolver [Member]	Sep. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Solar Revolver [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member]	Mar. 14, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member] Commercial Paper [Member]	Oct. 18, 2013 Commonwealth Edison Co [Member] SubsequentEventTypeMember [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member] Syndicated Revolver [Member]		Sep. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] Fixed Rate Debt [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] Fixed Rate Debt [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] Fixed Rate Debt [Member] First Mortgage Bonds 7.500% July1,2013 [Member]	Sep. 30, 2013 PECO Energy Co [Member]	Aug. 30, 2013 PECO Energy Co [Member]	Aug. 10, 2013 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]	Oct. 18, 2013 PECO Energy Co [Member] SubsequentEventTypeMember [Member]	Sep. 30, 2013 PECO Energy Co [Member] Syndicated Revolver [Member]		Sep. 30, 2012 PECO Energy Co [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member] First And Refunding Mortgage Bonds, 2.375% September 15, 2022 [Member]	Sep. 30, 2013 PECO Energy Co [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member] First And Refunding Mortgage Bonds 1200 October 15, 2016 [Member]	Sep. 30, 2013 PECO Energy Co [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member] First And Refunding Mortgage Bonds 4800 October 15, 2043 [Member]	Oct. 15, 2013 PECO Energy Co [Member] Long Term Debt Retirements [Member] Fixed Rate Debt [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member]	Aug. 10, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] Commercial Paper [Member]	Oct. 18, 2013 Baltimore Gas and Electric Company [Member] SubsequentEventTypeMember [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] Syndicated Revolver [Member]		Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Issuances [Member] Senior Notes [Member]	Oct. 01, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, 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, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Senior Notes [Member] Fixed Rate Debt [Member] Senior Notes 6.125% July1,2013 [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										1.000											1.075
Bilateral letters of credit																75,000,000
Amount Of Aggregate Letters of Credit Available																																																	500,000,000
Revolver Under Amendment		500,000,000													5,300,000,000																																		1,000,000,000											600,000,000										600,000,000
Accounts Receivable Agreement [Abstract]
Short-term notes payable - accounts receivable agreement	0		210,000,000																																																										210,000,000
Accounts receivable, principal payment																																																											210,000,000
Gross accounts receivable pledged as collateral	0		289,000,000																																																										289,000,000
AVSR Project Development Debt Agreement [Abstract]
DOE loan guarantee														646,000,000
Generation letters of credit outstanding to support project														327,000,000
Capital Lease Obligations [Abstract]
Capital Lease term																																																20 years
CapitalLeaseObligationsIncurred																																																1,000,000
CapitalLeaseObligations																																																8,000,000
Long-Term Debt [Abstract]
Long-term debt to affiliate														1,528,000,000			2,007,000,000
Non-Recourse Debt - MW					667
Non-Recourse Debt - Interest Rate Swap																											350,000,000
Total long-term debt																																																																				300,000,000
Long-term debt	17,583,000,000		17,190,000,000									2,000,000	442,000,000	5,545,000,000			5,245,000,000											43,000,000		38,000,000	523,000,000	788,000,000	613,000,000		100,000,000	9,000,000	450,000,000	2,000,000	46,000,000	3,000,000	1,000,000	75,000,000	2,000,000	450,000,000	[1]	18,000,000	13,000,000	5,057,000,000		5,315,000,000					350,000,000	125,000,000	127,000,000	2,196,000,000			1,647,000,000				350,000,000	300,000,000	250,000,000		1,746,000,000		1,446,000,000					250,000,000	300,000,000	34,000,000	33,000,000	31,000,000	110,000,000	400,000,000
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												7.30%	7.60%															1.99%		2.50%	4.25%	5.60%	6.00%			4.40%	6.15%	7.83%	5.00%	2.27%	2.563%		7.83%	8.625%	[1]		2.49%								4.60%	7.625%	7.50%								2.375%	1.20%	4.80%	5.60%								2.80%	3.35%	5.72%	5.72%	5.68%		6.125%
Minimum interest rate on long-term debt																													2.21%					2.535%	2.33%											1.93%																																			6.73%
Maximum interest rate on long-term debt																													2.44%					3.353%	3.092%											1.95%																																			6.75%
Long Term Debt																													5,000,000					204,000,000
Gain from exchange offer																											26,000,000
Derivative, Gain on Derivative						2,000,000	4,000,000	1,000,000
DebtInstrumentCollateralAmount	1,800,000,000
Footnotes To Long-Term Debt [Abstract]
Capital Lease Obligations Noncurrent																																																7,000,000
Notional amount of interest rate cash flow hedge derivatives									1,100,000,000	650,000,000															38,000,000	134,000,000
Line Of Credit Facility [Abstract]
Aggregate bank commitments under unsecured revolving credit facilities	8,400,000,000			500,000,000														50,000,000	5,300,000,000	[2]	10,000,000	300,000,000	100,000,000																													34,000,000	1,000,000,000	[2]								34,000,000	600,000,000	[2]									5,000,000	600,000,000	[2]
Actual available capacity																								131,000,000
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														24,000,000										90,000,000																								26,000,000										21,000,000											1,000,000
Short Term Debt [Line Items]
Commercial paper borrowings																																																			$ 153,000,000																					$ 40,000,000

[1] Represents debt obligations assumed by Exelon as part of the merger on March 12, 2012 that became callable at face value on June 15, 2013. Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable as of December 31, 2012 included in long-term debt to affiliate on Generation’s Consolidated Balance Sheets and notes receivable from affiliates at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets. The third-party debt obligations were reported in Long-term Debt on Exelon’s Consolidated Balance Sheets as of December 31, 2012. The debentures were redeemed and the intercompany loan agreements repaid on June 15, 2013.

[2] Excludes additional credit facility agreements for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million, $34 million, $34 million and $5 million, respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. These facilities expire on October 18, 2014 and are solely utilized to issue letters of credit. As of September 30, 2013, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $24 million, $26 million, $21 million and $1 million, respectively.