Debt and Credit Agreements - Schedule of Issuance of Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Convertible Debt Securities [Member]	Jun. 11, 2014 Convertible Debt Securities [Member]	Sep. 30, 2014 Long Term Debt Issuances [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] UpstreamGasLending221July222016[Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] NuclearFuelPurchaseContract3350june302018 [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Unsecured Debt [Member] NuclearFuelPurchaseContract3350june302018 [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Unsecured Debt [Member] ExgenRenewablesI425June62021[Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Unsecured Debt [Member] Energy Efficiency Project Financing [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Unsecured Debt [Member] AVSR [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Unsecured Debt [Member] NuclearFuelPurchaseContract3250june302018Member [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] Energy Efficiency Project Financing [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] NuclearFuelPurchaseContract3250june302018Member [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] ExGen Texas Power [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] Continental Wind 6000 February 28, 2033 [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstMortgageBondSeries115January152019 [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstMortgageBondSeries116January152044 [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstMortgageBondSeries114August152043 [Member] [Member]	Sep. 30, 2014 PECO Energy Co [Member]	Dec. 31, 2013 PECO Energy Co [Member]	Sep. 30, 2014 PECO Energy Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstAndRefundingMortageBondsOctoberu12044 [Member]	Sep. 30, 2013 PECO Energy Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstAndRefundMortgageBondOctober152016 [Member]	Sep. 30, 2013 PECO Energy Co [Member] Long Term Debt Issuances [Member] First Mortgage Bonds [Member] FirstAndRefundMortgageBondOctober152043 [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Issuances [Member] Senior Notes [Member] SeniorNotesJuly12023Member [Member]	Sep. 30, 2013 Floating Rate Debt [Member] 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, 2013 Floating Rate Debt [Member] Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member] CEU Credit Agreement [Member]
Debt Instrument [Line Items]
Interest Rate					2.50%				3.35%						4.12%	3.25%		6.00%			2.15%	4.70%	4600000.00%			4.15%	1200000.00%	4800000.00%			3350000.00%		4.40%
Long-term Debt	$ 131			$ 1,150				$ 5		$ 38	$ 300	$ 12	$ 125	$ 32			$ 675	$ 613			$ 300	$ 350	$ 350			$ 300	$ 300	$ 250			$ 300
Long-term Debt, Excluding Current Maturities	19,200	17,623				6,741	5,645												5,448	5,058				2,246	1,947				1,904	1,941		204	9
Subordinated Debt, Amount			$ 1,150