Debt and Credit Agreements - Schedule of Issuance of Long-Term Debt (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Debt Instrument [Line Items]
Interest Rate	4.10%
Debt Instrument, Face Amount		$ 750
Proceeds from (Repayments of) Other Long-term Debt	$ (30)	0
SeniorUnsecured245April2021 [Member]
Debt Instrument [Line Items]
Interest Rate	2.45%
Debt Instrument, Face Amount	$ 300
SeniorUnsecured340April2026 [Member]
Debt Instrument [Line Items]
Interest Rate	3.40%
Debt Instrument, Face Amount	$ 750
SeniorUnsecured445April2046 [Member]
Debt Instrument [Line Items]
Interest Rate	4.45%
Debt Instrument, Face Amount	$ 750
Exelon Generation Co L L C [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate	1.43%
Debt Instrument, Face Amount	$ 86
Exelon Generation Co L L C [Member] | EscoNotes390February2018 [Member]
Debt Instrument [Line Items]
Interest Rate	3.40%
Debt Instrument, Face Amount	$ 13
Exelon Generation Co L L C [Member] | DominionFederal [Member]
Debt Instrument [Line Items]
Interest Rate	0.00%
Debt Instrument, Face Amount	$ 16
Exelon Generation Co L L C [Member] | NonrecourseDebtSeptember2036 [Member]
Debt Instrument [Line Items]
Interest Rate	3.90%
Debt Instrument, Face Amount	$ 150
Exelon Generation Co L L C [Member] | NonrecourseDebtSeptember2019Member [Member]
Debt Instrument [Line Items]
Interest Rate	4.80%
Debt Instrument, Face Amount	$ 4
Exelon Generation Co L L C [Member] | DOE Financing Project [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150
Commonwealth Edison Co [Member] | FirstMortgageBonds120 [Member]
Debt Instrument [Line Items]
Interest Rate	2.55%
Debt Instrument, Face Amount	$ 500
Commonwealth Edison Co [Member] | FirstMortgageBonds121 [Member]
Debt Instrument [Line Items]
Interest Rate	3.65%
Debt Instrument, Face Amount	$ 700
PECO Energy Co [Member]
Debt Instrument [Line Items]
Proceeds from (Repayments of) Other Long-term Debt	$ (30)	$ 0
PECO Energy Co [Member] | FirstMortgageBondsSeptember2021 [Member]
Debt Instrument [Line Items]
Interest Rate	1.70%
Debt Instrument, Face Amount	$ 0
Potomac Electric Power Company [Member] | EscoNotes330August2017 [Member]
Debt Instrument [Line Items]
Interest Rate	3.50%
Debt Instrument, Face Amount	$ 11
Potomac Electric Power Company [Member] | ESCONotesDOEGDecember2017 [Member]
Debt Instrument [Line Items]
Interest Rate	3.30%
Debt Instrument, Face Amount	$ 2
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Proceeds from (Repayments of) Other Long-term Debt	(190)
Baltimore Gas and Electric Company [Member] | SeniorNotesAugust2046 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	500
Baltimore Gas and Electric Company [Member] | SeniorNotesAugust2026Member [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350
Baltimore Gas and Electric Company [Member] | Notes Payable, Other Payables [Member] | SeniorNotesAugust2046 [Member]
Debt Instrument [Line Items]
Interest Rate	3.50%
Baltimore Gas and Electric Company [Member] | Notes Payable, Other Payables [Member] | SeniorNotesAugust2026Member [Member]
Debt Instrument [Line Items]
Interest Rate	2.40%