Debt and Credit Agreements - Schedule of Issuance of Long-Term Debt (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Long-term Debt		$ 131
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],[2]	$ 1,250
Senior Notes [Member] | MergerDebt495June152035 [Member]
Debt Instrument [Line Items]
Interest Rate		4.95%
Debt Instrument, Face Amount	[1],[2]	$ 500
Senior Notes [Member] | MergerDebt510June152045 [Member]
Debt Instrument [Line Items]
Interest Rate		5.10%
Debt Instrument, Face Amount	[1],[2]	$ 1,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 4,200
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]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 3,200
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 39
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		2.96%
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[3]	$ 435
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.50%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		2.70%
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[4]	$ 750
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	[4]	$ 750
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExGen425Feb062021 [Member]
Debt Instrument [Line Items]
Interest Rate			4.44%
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		$ 50
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] | Subordinated Debt [Member] | JuniorNotes250June012024 [Member]
Debt Instrument [Line Items]
Interest Rate			2.50%
Debt Instrument, Face Amount			$ 1,150
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member]
Debt Instrument [Line Items]
Interest Rate			3.35%
Debt Instrument, Face Amount			$ 38
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

[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 2025 notes, the 2035 notes and the 2045 notes must be redeemed upon the earlier of (i) December 31, 2015, if the PHI acquisition is not consummated on or prior to such date, or (ii) the date on which the Merger Agreement relating to the PHI acquisition is terminated.

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

[4] 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.