Debt and Credit Agreements (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended						1 Months Ended	3 Months Ended	6 Months Ended		1 Months Ended						3 Months Ended			6 Months Ended															6 Months Ended															3 Months Ended		6 Months Ended										3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Apr. 02, 2014	Dec. 31, 2013	Jun. 30, 2014 Maximum [Member]	Jun. 30, 2014 Minimum [Member]	Jun. 30, 2014 BridgeLoanMember	Jun. 30, 2014 Designated as Hedging Instrument [Member] Interest Rate Swap [Member] Fair Value Hedging [Member]	Jun. 30, 2014 Designated as Hedging Instrument [Member] Interest Rate Swap [Member] Fair Value Hedging [Member]	Dec. 31, 2013 Designated as Hedging Instrument [Member] Interest Rate Swap [Member] Fair Value Hedging [Member]	Jun. 30, 2014 convertible debt member	Jun. 30, 2014 Long Term Debt Issuances [Member]	Jun. 30, 2013 Long Term Debt Issuances [Member] Suboridanted Debentures [Member]	Jun. 30, 2014 Exelon Corporate [Member]	Jun. 30, 2014 Exelon Corporate [Member] Syndicated Revolver [Member]	Jun. 30, 2014 Exelon Corporate [Member] Letter of Credit [Member] DebtInstrumentRedemptionPeriodThreeMember	Jun. 30, 2014 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]		Jun. 30, 2014 Exelon Generation Co L L C [Member]		Jun. 30, 2013 Exelon Generation Co L L C [Member]		Dec. 31, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Commercial Paper [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Letter of Credit [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Letter of Credit [Member] DebtInstrumentRedemptionPeriodOneMember	Jun. 30, 2014 Exelon Generation Co L L C [Member] Letter of Credit [Member] DebtInstrumentRedemptionPeriodTwoMember	Jun. 30, 2014 Exelon Generation Co L L C [Member] Designated as Hedging Instrument [Member] Foreign Exchange Contract [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] ExgenRenewablesI425June62021[Member] Interest Rate Swap [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] CEU Credit Agreement [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] UpstreamGasLending221July222016[Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] NuclearFuelPurchaseContract3.350%June302018 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member]	Jun. 30, 2013 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, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member] Floating Rate Debt [Member] DOE Project Financing, 3.092% January 2, 2037 [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Non Recourse Debt [Member] ExgenRenewablesI425June62021[Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Armstrong Co Tax Exempt, 5% December 1,2042 [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Sacramento PV Energy [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Clean Horizons [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] MEDCO Tax-Exempt Bonds [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Continental Wind 6000 February 28, 2033 [Member] Continetal Wind [Member]	Jun. 30, 2014 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]	Jun. 30, 2013 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]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Senior Notes [Member] SeniorSecuredNotes525January152014Member [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Pollution Control Notes [Member] Fixed Rate Debt [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Mar. 14, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Commercial Paper [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Syndicated Revolver [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstMortgageBondSeries215January152019 [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstMortgageBondSeries47January152044Member [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] FirstMortgageBond163January12014 [Member]	Jun. 30, 2014 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] Pollution Control Notes [Member] Fixed Rate Debt [Member]	Jun. 30, 2014 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Jun. 30, 2014 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Dec. 31, 2013 PECO Energy Co [Member]	Jun. 30, 2014 PECO Energy Co [Member] Syndicated Revolver [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Commercial Paper [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Syndicated Revolver [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Issuances [Member] Senior Notes [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Medium Term, Notes 6.73% 6.75% June 15, 2012 [Member]
Long-Term Debt [Abstract]
Long-term debt to affiliate																				$ 948,000,000			$ 948,000,000				$ 1,523,000,000
Non-Recourse Debt - Interest Rate Swap																																		240,000,000
Long-term debt to PECO Energy Transition Trust due within one year																				563,000,000			563,000,000
Long-term debt to financing trusts	648,000,000	648,000,000		648,000,000			648,000,000																																														206,000,000		206,000,000		206,000,000								184,000,000		184,000,000		184,000,000		258,000,000		258,000,000		258,000,000
Interest rate on long-term debt															2.50%																				4.40%	2.21%	3.35%				4.25%				2.56%	2.56%		6.00%	7.83%		5.35%	4.10%									2.15%	4.70%	1.63%	5.85%														3.35%	5.72%
Minimum interest rate on long-term debt																																						2.33%	0.02535%
Maximum interest rate on long-term debt																																						3.092%	0.02922%
Long Term Debt	131,000,000	131,000,000		131,000,000																1,000,000			1,000,000													3,000,000	38,000,000				300,000,000	3,000,000			1,000,000	1,000,000		11,000,000	2,000,000		500,000,000	20,000,000									300,000,000	350,000,000	600,000,000	17,000,000															35,000,000
Derivative, Gain on Derivative			3,000,000		4,000,000						3,000,000	5,000,000								2,000,000	2,000,000	[1]	1,000,000	[1]	1,000,000	[1]
DebtInstrumentCollateralAmount	1,900,000,000	1,900,000,000		1,900,000,000
Long-term Debt, Excluding Current Maturities	18,133,000,000	18,133,000,000		18,133,000,000			17,623,000,000													5,944,000,000			5,944,000,000				5,645,000,000								9,000,000			300,000,000		197,000,000			450,000,000	125,000,000			33,000,000			1,000,000			5,448,000,000		5,448,000,000		5,058,000,000								1,947,000,000		1,947,000,000		1,947,000,000		1,904,000,000		1,904,000,000		1,941,000,000					6,000,000	1,000,000
Footnotes To Long-Term Debt [Abstract]
Notional amount of interest rate cash flow hedge derivatives											1,400,000,000	1,400,000,000	1,275,000,000																			121,000,000	257,000,000
Line Of Credit Facility [Abstract]
LineOfCreditFacilityMaximumBorrowingCapacity	8,500,000,000	8,500,000,000		8,500,000,000														500,000,000																																										1,000,000,000										600,000,000							600,000,000
Outstanding letters of credit																			100,000,000										100,000,000	300,000,000	100,000,000
Footnotes To Line Of Credit Facility [Abstract]
Credit facility agreements with minority and community banks																				50,000,000			50,000,000																														34,000,000		34,000,000										34,000,000		34,000,000				5,000,000		5,000,000
Letters of credit																				20,000,000			20,000,000																														17,000,000		17,000,000										21,000,000		21,000,000				1,000,000		1,000,000
ShortTermBorrowingsAbstract
Commercial paper borrowings																												0																															498,000,000																	70,000,000
Short-term debt outstanding amount	621,000,000	621,000,000		621,000,000			341,000,000													53,000,000			53,000,000				22,000,000																										498,000,000		498,000,000		184,000,000														70,000,000		70,000,000		135,000,000
BridgeLoan	4,200,000,000	4,200,000,000		4,200,000,000		7,200,000,000
Interest Expense		228,000,000	246,000,000	445,000,000	863,000,000					9,000,000										74,000,000	77,000,000		147,000,000		142,000,000																												76,000,000	72,000,000	153,000,000	422,000,000									25,000,000	25,000,000	50,000,000	51,000,000			23,000,000	28,000,000	47,000,000	58,000,000
Credit Agreements [Abstract]
Additional amounts available upon request under current credit facilities																																																										500,000,000
Basis points adders for prime-based borrowings																	0.275			0.275			0.275																														0.075		0.075										0		0				0		0
Basis points adders for LIBOR-based borrowings																	1.275			1.275			1.275																														1.075		1.075										0.900		0.900				1		1
Amount Of Aggregate Letters of Credit Available																																																										500,000,000
Revolver Under Amendment																																																										1,000,000,000
Equity Securities Offering [Abstract]
EquitySecuritiesOfferingTotalNumber	57,500,000
Share Price	$ 35	$ 35		$ 35
UnderwritingDiscount	60,000,000	60,000,000		60,000,000
underwriting fees	35,000,000
Proceeds from the issuance of subordinate debt														1,100,000,000
SubordinatedLongTermDebt														1,200,000,000		1,150,000,000
Coupon rate of interest on Equity Unites	2.50%
ForwardContractPaymentRate	4.40%
Per unit conversion rate for Equity Security units	$ 33.96	$ 33.96		$ 33.96										$ 50
Shares issueable at June 30, 2014 ifsettlement occurred	4,000,000	4,000,000		4,000,000
CommonSharesIssueableAt Maturity								1.4286	1.1429
Shares to be used in Physical settlement	57,700,000
Proceeds at forward price								$ 1,950,000,000	$ 1,850,000,000
Daily accretion rate less spread	0.75%	0.75%		0.75%
Exelon's Stock Price At Maturity								$ 43.75	$ 35.00

[1] For the three and six months ended June 30, 2014, the loss on Generation swaps included $4 million and $8 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. For the three and six months ended June 30, 2013, the loss on Generation swaps included $4 million and $8 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing.