Debt and Credit Agreements - Schedule of Issuance of Long-Term Debt (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Oct. 15, 2015	Oct. 05, 2015	Sep. 30, 2014	Jun. 11, 2014	May. 01, 2014
Debt Instrument [Line Items]
Long-term Debt						$ 131
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage		1.00%
Unamortized Debt Issuance Expense		$ 22
Senior Notes [Member] | MergerDebt155June092017 [Member]
Debt Instrument [Line Items]
Interest Rate		1.55%
Debt Instrument, Face Amount	[1]	$ 550
Senior Notes [Member] | MergerDebt285June152020 [Member]
Debt Instrument [Line Items]
Interest Rate		2.85%
Debt Instrument, Face Amount	[1]	$ 900
Senior Notes [Member] | MergerDebt395June152025 [Member]
Debt Instrument [Line Items]
Interest Rate		3.95%
Debt Instrument, Face Amount	[1]	$ 1,250
Senior Notes [Member] | MergerDebt495June152035 [Member]
Debt Instrument [Line Items]
Interest Rate		4.95%
Debt Instrument, Face Amount	[1]	$ 500
Senior Notes [Member] | MergerDebt510June152045 [Member]
Debt Instrument [Line Items]
Interest Rate		5.10%
Debt Instrument, Face Amount	[1]	$ 1,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							$ 4,200
Subordinated Debt [Member] | JuniorNotes250June012024 [Member]
Debt Instrument [Line Items]
Interest Rate					2.50%
Debt Instrument, Face Amount					$ 1,150
Notes Payable, Other Payables [Member] | SoftwareLicense395May012024 [Member]
Debt Instrument [Line Items]
Interest Rate		3.95%
Debt Instrument, Face Amount		$ 111
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 39			$ 125
Exelon Generation Co L L C [Member] | AVSR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate		2.96%			3.14%
Exelon Generation Co L L C [Member] | AVSR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate		2.29%			3.06%
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[2]	$ 435
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate		2.70%
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate		2.50%
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate					4.40%
Debt Instrument, Face Amount	[3]	$ 750
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate					5.25%
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate		3.71%
Debt Instrument, Face Amount		$ 42
Exelon Generation Co L L C [Member] | Senior Notes [Member] | EnergyEfficiency355Nov152016 [Member]
Debt Instrument [Line Items]
Interest Rate		3.55%
Debt Instrument, Face Amount		$ 19
Exelon Generation Co L L C [Member] | Senior Notes [Member] | SeniorNotesJuly12023Member [Member]
Debt Instrument [Line Items]
Interest Rate		2.95%
Debt Instrument, Face Amount	[3]	$ 750
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExGen425Feb062021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 300
Exelon Generation Co L L C [Member] | Senior Notes [Member] | AGE143Nov172017 [Member]
Debt Instrument [Line Items]
Interest Rate		1.43%
Debt Instrument, Face Amount		$ 74
Exelon Generation Co L L C [Member] | Unsecured Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate					4.94%
Debt Instrument, Face Amount					$ 675
Exelon Generation Co L L C [Member] | Unsecured Debt [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate					4.12%
Debt Instrument, Face Amount					$ 12
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate		5.25%			4.44%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Interest Rate			5.25%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate		4.94%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | Continental Wind 6000 February 28, 2033 [Member]
Debt Instrument [Line Items]
Interest Rate		6.00%			6.00%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 70
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate					3.35%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate					3.25%
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBondSeries115January152019 [Member]
Debt Instrument [Line Items]
Interest Rate					2.15%
Debt Instrument, Face Amount					$ 300
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBondSeries116January152044 [Member]
Debt Instrument [Line Items]
Interest Rate					4.70%
Debt Instrument, Face Amount					$ 350
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBondSeries118March12045 [Member]
Debt Instrument [Line Items]
Interest Rate		3.70%
Debt Instrument, Face Amount		$ 400
PECO Energy Co [Member] | First Mortgage Bonds [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Long-term Debt				$ 350
Interest Rate				3.15%
PECO Energy Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBond101 [Member]
Debt Instrument [Line Items]
Interest Rate					4.15%
Debt Instrument, Face Amount					$ 300

[1] In connection with the issuance of PHI acquisition financing, Exelon terminated its interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further informatio

[2] The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020.

[3] In connection with the issuance of Senior Unsecured Notes, Exelon terminated floating-to-fixed interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information on the swap termination.