Debt and Credit Agreements - Issuance of Long-Term Debt (Details) - USD ($)		3 Months Ended	9 Months Ended
		Sep. 30, 2017	Sep. 30, 2014	Jun. 30, 2014
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest Rate		3.497%		2.50%
JSNotes350June2022 [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest Rate	[1]	3.50%
Debt Instrument, Face Amount		$ 1,150,000,000
PECO Energy Co [Member] | FRMB370Sep2047 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		3.70%
Debt Instrument, Face Amount		$ 325,000,000
Exelon Generation Co L L C [Member] | EEPFNotes372April2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate		3.72%
Debt Instrument, Face Amount		$ 4,000,000
Exelon Generation Co L L C [Member] | EEPF261Sep2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate		2.61%
Debt Instrument, Face Amount		$ 10,000,000
Exelon Generation Co L L C [Member] | EEPFNotes390Jan2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate		3.90%
Debt Instrument, Face Amount		$ 17,000,000
Exelon Generation Co L L C [Member] | AGEPFNotesNov2017 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 14,000,000
Debt Instrument, Interest Rate Terms		LIBOR + 1.25%
Exelon Generation Co L L C [Member] | SeniorUnsecured295Jan2020 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate		2.95%
Debt Instrument, Face Amount		$ 250,000,000
Exelon Generation Co L L C [Member] | EEPF353Apr2019 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate		3.53%
Debt Instrument, Face Amount		$ 8,000,000
Exelon Generation Co L L C [Member] | SeniorUnsecured340Mar2022 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate		3.40%
Debt Instrument, Face Amount		$ 500,000,000
Exelon Generation Co L L C [Member] | EGTP475Sep2021 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 6,000,000
Debt Instrument, Interest Rate Terms		LIBOR + 4.75%	LIBOR plus 4.75%
Commonwealth Edison Co [Member] | FMB295Aug2027 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		2.95%
Debt Instrument, Face Amount		$ 350,000,000
Commonwealth Edison Co [Member] | FMB375Aug2047 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		3.75%
Debt Instrument, Face Amount		$ 650,000,000
Baltimore Gas and Electric Company [Member] | Notes375Aug2047 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate		3.75%
Debt Instrument, Face Amount		$ 300,000,000
Potomac Electric Power Company [Member] | FMB415Mar2043 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		4.15%
Debt Instrument, Face Amount		$ 200,000,000
Potomac Electric Power Company [Member] | EEPFNotes330December2017 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate		3.30%
Debt Instrument, Face Amount		$ 2,000,000

[1] (a)See the Junior Subordinated Notes discussion below for further information.