Debt and Credit Agreements - Issuance of Long-Term Debt (Details)	Mar. 31, 2018 USD ($)
Exelon Generation Co L L C [Member] | EEPF372Apr2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.72%
Debt Instrument, Face Amount	$ 1,000,000
Exelon Generation Co L L C [Member] | EEPF317Apr2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.17%
Debt Instrument, Face Amount	$ 1,000,000
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	$ 2,000,000
Commonwealth Edison Co [Member] | FMB400Mar2048Member | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate	4.00%
Debt Instrument, Face Amount	$ 800,000,000
PECO Energy Co [Member] | FRMB390Mar2048 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate	3.90%
Debt Instrument, Face Amount	$ 325,000,000